Economy:
This section deals with all basic facts about economy. We talk little bit about worls econmy and then go in more detail about US economy, since there is lot of data available for US economy:
1. World population
2. World GDP
3. USA GDP
4. USA banks
5. USA hosuing
.....
ARM microcontrollers use proprietery bus i/f both to communicate internally as well as externally. This proprietery bus i/f is based on AMBA spec. The Advanced Microcontroller Bus Architecture (AMBA) specification defines an onchip communications standard for designing high-performance embedded microcontrollers.
Many distinct buses are defined within the AMBA specification. Some of these are:
• the Advanced High-performance Bus (AHB)
• the Advanced Peripheral Bus (APB).
* AXI Bus
AMBA based ARM microcontrollers use AHB as the cpu bus, which connects to high speed devices as memory, and also connected to to a bridge which is connected to a lower b/w APB bus, where most of peripheral devices are connected.
AHB:
AHB is the main bus connecting processor to memory and other high speed devices. This is the bus you see coming out of cortex processor to connect to other devices.
Cortex M3 is the first cortex family processor. It supports T32 ISA.
Cortex M3 has 2 operation modes: thread mode (when running a normal pgm) and handler mode (when running an exception handler). It also has 2 privilege levels: privileged state (where it has all privileged rights incl access to all mem range and all reg), and user state (where it has access to limited mem range and reg to prevent user pgm from causing system crash).
When M3 exits from reset, it starts in privileged mode. The pgm then writes a control reg to switch M3 to user state. Once in user state, the pgm there can't write control reg to switch it back to privilege state. Thus it's one way switch from privilege state to user state. The only time when user pgm can enter privilege state, is when it gets an exception and switches to handler mode. Then while the exception code is running, M3 is in privilege state (to allow exceptions to access all mem and all reg as they are trusted pgm, and usually need unrestricted access), and switches back to user state when switching to thread mode.
FIXME => more info
Deals 2021:
Here are the archived deals from 2021. For most recent deals goto DEALS
For deals from 2020, goto DEALS 2020
2021:
12/31/2021: Walgreens 8x10 Free photo - Code ZERO
Look in "photo" under shopping section for details of the offer: photo
12/25/2021: Walgreens 8x10 Free photo - Code FROSTY8X10
Look in "photo" under shopping section for details of the offer: photo
12/12/2021: Walgreens 5 Free 4x6 photo - Code 5FREEPRINT
Look in "photo" under shopping section for details of the offer: photo
12/03/2021: Walgreens 8x10 Free photo - Code MERRY8X10
Look in "photo" under shopping section for details of the offer: photo
12/01/2021: Taco bell GC offer - 1 free combo per $25 in store, 10% off for online (expires 25th Dec, 2021):
Look in gift card section for details of the offer: gift cards
https://www.tacobell.com/online-gift-card-promotion-terms-and-conditions
12/01/2021: Taco Bell Offer: 24 days of free cravings with a purchase of $1+ on app - Valid 30th Nov, 2021 to 23rd Dec, 2021
One free purchase every day with $1+ purchase on app. Has to be a reward member, which is free to join. Deals are posted every day, check the link every day. Use the taco bell GC offer along with this.
11/26/2021: Newegg - 2 X 8gb DDR 4 memory sticks for $47
Look in "electronics" under shopping section for details of the offer: electronics
11/26/2021: Walgreens 8x10 Free photo - Code THANKFUL8X10
Look in "photo" under shopping section for details of the offer: photo
11/25/2021: HEB Gift Card Offer (in Texas stores only) - Buy Home Depot, Kohls, Academy, Childrens's Place, Vanilla Visa $100 GC, get $20 HEB GC free for each (expires 30th Nov, 2021):
Look in gift card section for details of the offer: gift cards
11/22/2021: American Express 20% discount on redeeming points for Gift cards: (valid until Dec 22, 2021)
This is one of the best sign on bonus. See in "credit cards" section: credit cards
11/22/2021: Platinum Elite Visa Credit Card from Skyone with $600 sign on bonus (valid until Dec 31, 2021)
This is one of the best sign on bonus. See in "credit cards" section: credit cards
11/16/2021: Slickdeals $10 cashback on $25+ Macy's online purchase => expires 11/16/2021
Look in "cash back sites" section for details of the offer: cash back sites
11/14/2021: Walmart - Cordless hair trimmer for $17
It's cordless, works worldwide (100V-240V), and has lots of good reviews. If you find it cheaper anywhere else within 90 days, you can just return and rebuy. You can get really cheap ones for < $10 on sale once in a while in pharmacy sores, but I don't think you can get these quality ones for $17 anywhere. One haircut and you have recovered your investment !!
11/14/2021: Walgreens 8x10 Free photo - Code GRATEFUL8X10
Look in "photo" under shopping section for details of the offer: photo
11/14/2021: Walmart - 256 GB USB 3.0 flash drive for $20
Look in "electronics" under shopping section for details of the offer: electronics
11/12/2021: Walgreens 5X7 Free photo - Code IGOTMYSHOT => expires in couple of days
Look in "photo" under shopping section for details of the offer: photo
11/10/2021: M1 Finance Brokerage Bonus Offer of $500 - expires Dec 31st, 2021
Look in brokerage account bonus section for details of the offer: best brokerage bonus
11/07/2021: Walgreens Offer - Multiple items for almost free (after Walgreens cash) at Walgreens for week of 11/07/21 to 11/13/21
This deal will have all below items for $5 or so, if you have the coupon "$5 WGC on $20+". This offer is there on many accounts, so look up in your account under coupons. Below are individual deals. You can mix and match to take the total above $20 after applying coupon FAST10 (but before applying any Manufacturer coupons (Man-Q), as the total can be below $20 after Man-Q, and still be elgible for $5 in WGC.
have multiple deals for this week. Some people also have an extra coupon in their account for $5 WGC for spending $20+, or $4 WGC for spending $25+. I'm listing items that will add up to $25 before manufacturer coupons. It has been confirmed that total before Manufacturer coupon count toward the total for reward purpose.
The links below are for each deal separately. Choose the ones you like.
1. Colgate for free: 1 for free after $2 coupon
https://slickdeals.net/f/15382471-walgreens-free-colgate-toothpaste
2. Razor for a $1 after $5 coupon.
https://slickdeals.net/f/15382444-bic-disposable-razors-various-1-walgreens-w-free-shipping
3. 28 oz shampoo + conditioner for $3
4. 2 cereals for $3
5. 2 soaps for $1.30
6. 5 of 2L Pepsi bottles for $4 (not really cheap, as you can usually get them for < $1 a bottle on sale)
7. 80 count wipes for $1 (these can be used as a filler to meet $20 threshold). The wipes are good for cleaning fans, pantries, bathrooms, etc.
One possible combo is items 1, 2, 3, 4, 5 and 7 to get to over $20. After coupons price < $10 and you get $5 in WGC. So, effectively you are paying only $5 for all of these, which is as close to free as it can get !!
11/05/2021: Walgreens 8x10 Free photo - Code FALLSMILES
Look in "photo" under shopping section for details of the offer: photo
11/04/2021: Taco Bell Offer: Free Taco - Valid 4th Nov, 2021 only
Free locos taco offer is back. It says "A stolen base in the World Series™ won America a FREE Doritos® Locos Tacos. Get yours today online, on the app, or in-store." As last time, you can just walk in and get your free taco, or order online or via app.
11/01/2021: Tastyworks Brokerage Bonus Offer of $500 - expiry unknown
Look in brokerage account bonus section for details of the offer: best brokerage bonus
10/30/2021: Walgreens 8x10 Free photo - Code ONEBIG8X10
Look in "photo" under shopping section for details of the offer: photo
10/25/2021: Sofi Money account - ($75 via slickdeals or $175 via swagbucks) + $100 for direct deposit => expiry unknown
Look in bank account bonus section for details of the offer: best bank bonus
10/22/2021: Kabbage (by Amex) $300 Checking Account (Business) Bonus offer (Nationwide) => expires 12/15/2021
Look in bank account bonus section for details of the offer: best bank bonus
10/21/2021: YMMV: Chase Freedom Credit Card and Debit Card Offer - Cashback on using card at McDonalds, Exxon Mobil and Walgreens (expires in 2-6 days)
First activate the offers on your card by logging into Chase website, and clicking "chase offers" on right side. These special deals are listed as "Flash deals". Just click on them, you should see a green tickmark, meaning the offer is activated. Then buy $20 GC at McDonalds, $40 GC at Walgreens and get $50 of gas at Exxon Mobil. That maximizes your cashback to $4+$8+$10=$22. Most people are getting these offers, so do check in your chase account. Bed Bath and Beyond is useless offer, since you can get their GC at 20% discount any time, and their stuff is over priced by 2X or more compared to other stores.
10/15/2021: Topcashback mystery offer every Friday until Thanksgiving - $2.50 cb on $10= purchase => expires 11/29/2021
Look in "cash back sites" section for details of the offer: cash back sites
10/14/2021: Kroger Gift Card Offer online - Buy any $25 GC for $20 (expires 10/17/2021):
Look in gift card section for details of the offer: gift cards
10/10/2021: Fifth third Bank $300 Checking Bonus offer (only selected states => Florida, Georgia, Illinois, Indiana, Kentucky, Michigan, North Carolina, Ohio, South Carolina, Tennessee, and West Virginia) => expires 12/31/2021
Look in bank account bonus section for details of the offer: best bank bonus
09/22/2021: Amazon Warehouse Deals - Extra 40% on selected items (expiry unknown):
"40% off on used items" is the highest I've seen. However, amazon warehouse are not discounted that heavily to start with. So, research the price before falling for 40% off. Many of the items that I purchased before have gone up by 20% since last time, so 40% off gives you a litle worse deal than the 20% off from last time.
direct link: On clicking link below, you should see category as "Amazon Warehouse Deals". That shows all items for extra 40%. Now if you search for any item in this category, it will show only those items with extra 40% off. There will be sponsored items at top as well as items outside of this category at the bottom, do not click on those as those will take you out of "warehouse deals with 40% off". If you do so, you have again click the above "warehouse deals" link to get back.
https://www.amazon.com/s?i=warehouse-deals
09/21/2021: Walgreens 8x10 Free photo - Code 8X10AUTUMN
Look in "photo" under shopping section for details of the offer: photo
09/19/2021: OfficeDepot / OfficeMax - Free Non Rechargeable AA/AAA batteries after rewards (expires 09/25/2021):
Look in "electronics" under shopping section for details of the offer: electronics
09/06/2021: OfficeDepot / OfficeMax - Free Non Rechargeable AA/AAA batteries after rewards (expires 09/11/2021)
Look in "electronics" under shopping section for details of the offer: electronics
09/06/2021: 2.6Gbps Netgear router for $35 - at Walmart - OOS
Link below: very good price. It has 800Mbps speed on 2.4Ghz and 1.9Mbps speed on 5GHz band. It has 4 1Gbps Ethernet ports. Can't find any router with these specs for $35. Regular price for this is $100. Already out of stock by the time I checked out.
09/05/2021: Walgreens Offer - Multiple items for free (after Walgreens cash) at Walgreens for week of 09/05/21 to 09/11/21 (expires 09/11/2021):
You have multiple deals for this week. Some people also have an extra coupon in their account for $5 WGC for spending $20+, or $4 WGC for spending $25+. I'm listing items that will add up to $25 before manufacturer coupons. It has been confirmed that total before Manufacturer coupon count toward the total for reward purpose.
The links below are for each deal separately. Choose the ones you like.
1. Colgate for free: 2 for $4 + $4 WGC
2. Crest products for making $1: 3 dental products for #4 + $5 WGC
3. 12 count schick razors for $2:
4. Eye relief: 2 for $1.15
5. Quart sized or Gallon sized bags for $1 each. You get 50 quart sized or 20 gallon sized. These usually go on sale every month for this price. Add this item if Walgreens is out of stock of other items above.
Total for all these will be $27 (excluding item #5 above) before Man Coupons. $16 in Man Coupon, will take total to ~$11. total WGC cash will be around $9.
If you buy first 4 items above in a single order, you may use the coupon for $5 rewards on $20+ purchase (or $4 WGC on $25+). This coupon is available for almost all accounts, you just need to clip it, in order to apply to this order. Net cost will be about $2 Money maker with the $4 WGC coupon, not bad !!
09/05/2021: Subway Offer - BOGO (expires 11/05/2021): PROMO: FREESUB
https://slickdeals.net/f/15262693-subway-restaurant-buy-one-footlong-sub-get-one-footlong-sub
This offer is back, right after the previous one expired. It's same as what was offered last few times, and just like previous offers, runs for more than a month. It's buy one, get one free = effectively 2 subway for price of one. Can't beat the price. Need to order online or from app.
08/29/2021: Krispy Kreme Offer: 2 Free Doughnut per vaccination card for COVID - 08/30/21 (Monday) to 09/05/21 (Sunday)
Every day of the week, you can get 2 free doughnuts by showing your Covid-19 vaccination card. Pretty easy.
08/27/2021: Amazon Warehouse Deals - Extra 20% on selected items (expiry unknown):
https://slickdeals.net/f/15244558-20-off-amazon-warehouse-deals?src=frontpage
"20% off on used items" is back. It's coming more frequently than it used to. However, amazon warehouse are not discounted that heavily to start with. So, 20%
direct link: On clicking link below, you should see category as "Amazon Warehouse Deals". That shows all items for extra 20%. Now if you search for any item in this category, it will show only those items with extra 20% off.
https://www.amazon.com/s?i=warehouse-deals
Few good deals:
08/20/2021: Microcenter - Free 240 GB SSD drive, USB stick or MicroSD card (expiry unknown )
Look in "electronics" under shopping section for details of the offer: electronics
08/20/2021: Free entry to selected Museuums on Museum Day - September 18, 2021 (saturday) only
You have to print the ticket. 1 ticket per email address, which is good for 2 people. If you need more, you need to use other fake email addresses. Valid for Sept 18 only. Tickets to high demand museums get sold out pretty quick, so print your tickets first and think later.
08/18/2021: Walgreens 6 customized set of 5x7 Free photo - Code FREEHELLO => will expire soon.
Look in "photo" under shopping section for details of the offer: photo
08/15/2021: OfficeDepot / OfficeMax - Free Non Rechargeable AA/AAA batteries + select school supplies after rewards (expires 08/21/2021):=> OK offer
Look in "electronics" under shopping section for details of the offer: electronics
08/15/2021: Walgreens 8x10 Free photo - Code BIGGER8X10
Look in "photo" under shopping section for details of the offer: photo
08/06/2021: Exxon Mobil Oil Rebate: $5 to $15 per 5 quart oil, Limit 2 per household. Available at walmart for various prices => Runs from 6 months from 04/01/2021 to 09/30/2021
Look in "gasoline/oil deals" under Auto section for details of the offer: gasoline/oil deals
08/01/2021: OfficeDepot / OfficeMax - Free Non Rechargeable AA/AAA batteries after rewards (expires 08/07/2021):=> OK offer
Look in "electronics" under shopping section for details of the offer: electronics
08/01/2021: Amazon Warehouse Deals - Extra 20% on selected items (expiry unknown):
https://slickdeals.net/f/15194164-amazon-warehouse-20-discount-off-select-items
direct link: On clicking link below, you should see category as "Amazon Warehouse Deals". That shows all items for extra 20%. Now if you search for any item in this category, it will show only those items with extra 20% off.
https://www.amazon.com/s?i=warehouse-deals
I don't usually put link to generic sale, but this one deserves it's own thread. You can usually buy "like new" or "used good" items for about half off on Amazon warehouse. With extra 20% off select items, you can get even better deal. Few ex:
07/27/2021: Mochi Offer - Free box of bubbies mochi ice cream (expiry unknown):
https://slickdeals.net/f/15180019-free-box-of-bubbies-mochi-after-rebate-first-1000-us-only
rebate link:
https://bubbiesicecream.com/rebate
Free Box of Bubblies Mochi icecream. It's available at HEB grocery store, Whole Foods in Texas. It should be available at a lot of local grocery stores. People are successfully getting their mail in rebate amount credited. Requires paypal info. Doesn't look like their is limit of 1st 1000 buyers. Get it while you can !!
07/25/2021: Walgreens 8x10 Free photo - Code JULY8X10
Look in "photo" under shopping section for details of the offer: photo
07/25/2021: Walgreens Offer - Get 2 colgate toothpaste, crest toothpaste, mouthwash, toothbrush for free after walgreens rewards (expires 07/31/2021):
Again, free toothaste, mouthwash and toothbrush (after wags rewards). Can roll in rewards too.
07/022/2021: Taco Bell Offer: Free Taco - Valid 22nd July, 2021 only
Direct link: https://www.tacobell.com/nba-comebacks/
Free locos taco offer is back. It says flaming hot, but you can substitute it with anyhting. It was only on app/online for 21st July, but is in store too on 22nd July. As last time, you can just walk in and get your free taco, or order online or via app.
07/18/2021: OfficeDepot / OfficeMax - Free Non Rechargeable AA/AAA batteries after rewards (expires 07/24/2021):
Look in "electronics" under shopping section for details of the offer: electronics
07/14/2021: Whole Foods - Free Mochi Ice cream at Whole Foods via printable coupon (expires 08/31/2021):
Just answer simple simple questions, provide fake email, phone number and done !!
07/12/2021: OfficeDepot / OfficeMax - Free Non Rechargeable AA/AAA batteries after rewards (expires 07/17/2021):
Look in "electronics" under shopping section for details of the offer: electronics
EXPIRED: 07/12/2021: Subway Offer - BOGO (expires 09/03/2021): PROMO: FREEFOOTLONG
https://slickdeals.net/f/15158998-subway-buy-1-footlong-get-1-free?src=frontpage
This offer is back, same as what was offered last few times, and just like previous offers, runs for more than a month. It's buy one, get one free = effectively 2 subway for price of one. Can't beat the price. See below for details. Need to order online or from app.
EXPIRED: 07/04/2021: Walgreens Offer - Multiple items for free (after Walgreens cash) at Walgreens for week of 07/04/21 to 07/10/21 (expires 07/10/2021):
You have multiple deals for this week: The link below combines all the deals to get to $20 in total so that you can get $5 extra in Walgreens Cash. Even if you don't have $5 on $20+ coupon in your account, it's still a good deal for getting 7 items for $5 or so.
If you buy all 7 items above in a single order, you may use the coupon for $5 rewards on $20+ purchase. This coupon is available for almost all accounts, you just need to clip it, in order to apply to this order. Net cost will be about $0 for all the items if you include $10 walgreens cash reward.
NOTE: Even though the total is below $20 after coupons, the $5 reward is still triggered, based on the comments by SUCHaDEAL.
07/04/2021: Chipotle Offer: BOGO on 07/06/21 only for in store order from 3PM to close. - expires 07/06/21
In store only. Chipotle BOGO offers are rare, so putting up here. Just say "Friends BOGO" to the cashier to redeem the offer. Use Chipotle GC to pay, which you can usually accumulate at 20% off.
07/01/2021: BestBuy - Non Rechargeable 36 pack AA/AAA batteries for $6 (expires 07/01/2021 => valid only for 1 day):
Look in "electronics" under shopping section for details of the offer: electronics
06/30/2021: Walgreens Offer - Multiple deals at Walgreens for week of 06/27/21 to 07/03/21 (expires 07/03/2021):
You have multiple deals for this week:
1. Ladies Pads for $1 after $5 coupon.
2. BIC Flex5 razor for $1 after $5 rebate
3. Three Pringles for $2.70 => Use code SUMMER10 to knock 10% off
4. Three dozen cans of Coke/Pepsi for $9 => Use code SUMMER10 to knock 10% off
5. Tide detergent for $3 after $2 coupon => this coupon regularly available on walgreens
If you buy all 5 items above in a single order, you may use the coupon for $5 rewards on $20+ purchase. This coupon is available for almost all accounts, you just need to clip it, in order to apply to this order. Net cost will be about $10 for all the items if you include $5 reward + $5 MIR.
06/20/2021: ebay Offer - Used Cordless trimmer/Edger + blower for $42 (expiry unkown):
https://www.ebay.com/itm/353260279682
This is the cheapest cordless trimmer/edger you could find anywhere. A blower along with one battery+charger is included as well. The original price is $60, but there is extra 30% off for this merchant, which is applied at checkout. That brings the price down to $42. There was 10% cashback ongoing on topcashback.com, but as of 06/24, it's down to 1.5% (for purchases on ebay in home/garden category). New units sell on homedepot for $120 or more. It's used, but description says it's almost new. Will find out soon.
UPDATE 07/04/21: The cordless trimmer/edger and blower works well so far. Will need to wait for a year or more to see if the battery still holds up.
06/20/2021: CVS app Offer - Get free weekly gift on CVS app (expires 07/31/2021):
https://www.doctorofcredit.com/cvs-extracare-app-free-weekly-gift-6-20-7-31/
You get free weekly item. For the week of 06/20, it's nail clipper. Here's the list of free item for every week:
With 6 weeks in the offer, you get around 6 free items. Most of these items are worth about $1 each, so you are looking at max of $6 in free stuff. Personally I wouldn't do it, since it's like getting $6 for downloading the CVS app, and going to CVS every week. You can get $5 for downloading any app any day. Worth it only if you were already planning to go to CVS or have CVS within walking distance. Else gas will cost you more than these freebies - not a deal 
EXPIRED: 06/20/2021: Walgreens Offer - Get 2 colgate toothpaste for free after walgreens rewards (expires 06/26/2021):
You have $3 coupon, bringing the price to $3. With this coupon, you get 2 toothpaste for $3 and then $3 rewards, making it kind of free.
EXPIRED: 06/16/2021: HEB Gift Card Offer (in Texas stores only) - Buy Lowes $100 GC, Home Depot $100 GC or Academy $100 GC, get $15 HEB GC free (expires 06/22/2021):
Look in gift card section for details of the offer: gift cards
EXPIRED: 06/13/2021: Monifi $250 Checking Bonus offer => expires 06/30/2021
Look in bank account bonus section for details of the offer: best bank bonus
UPDATE: 06/20/2021: Multiple users reporting getting email for $100 now instead of $250.
EXPIRED: 06/06/2021: Walgreens Offer - Get BIC razor for $1 after coupon (expires 12th June, 2021 - will run out of stock fast !!):
https://slickdeals.net/f/15074926-bic-disposable-razors-packs-various-1-w-store-pickup
Any of the razors is a good choice here. One with 4 or 5 extra razors is a really good deal, as each razor costs 20 cents or so. My deal for razors is usually around 10 to 20 cents. There are no rewards involved, so that's even better.
06/06/2021: Hancock Whitney Bank $300 Checking Bonus offer (only valid in selected states). => expires 06/30/2021
Look in bank account bonus section for details of the offer: best bank bonus
EXPIRED: 06/02/2021: HEB Gift Card Offer (in Texas stores only) - Buy Lowes $100 GC or Home Depot $100 GC, get $20 HEB GC free (expires 8th May, 2021):
Look in gift card section for details of the offer: gift cards
EXPIRED: 05/31/2021: Walgreens Offer - Get two 8oz bags of Cashews for $2 (expiry unknown - will run out of stock fast !!):
Walgreens is killing the competition out there with their insane deals every week. This deal has no competition. You get about 450g of cashews (halves and pieces and not the whole cashews) for $1.88, implying a price of $4.2/kg. It's the cheapest you can get cashews anywhere in the world => whole cashew prices are currently $10/kg. cheapest variety of cashews are stll going to cost atleast $68/kg buying diretly from wholesale market. So, you are getting at least 50% off. These have a sell by date of June/July 2022, so hey are good for a year. Check the "sell by date" before you pick up your order. Don't order too many, as your order will get cancelled (as walgreens doesn't carry too many of any item). BTW, cashews pieces taste same as whole cashews, To be sure, I just tried both of them !!
05/31/2021: Comerica Bank $200 and $500 offer (only valid in TX and MI). => expiry unknown
Look in bank account bonus section for details of the offer: best bank bonus
EXPIRED: 05/09/2021: Walgreens Gift Card Offer - Buy Kohls 50 GC or Burlington $50 GC, get $10 Walgreens GC free (expires 15th May, 2021 - will run out of stock fast !!):
Look in gift card section for details of the offer: gift cards
EXPIRED: 05/09/2021: Walgreens Offer - Get two 6 oz Colgate toothpaste + three dozen Coke cans + 2 Stayfree Pads for $18 + get $9 in rewards (expires 15th May, 2021 - will run out of stock fast !!):
There are multiple offers at walgreens in this week's ad. Above is one possibility. You get everything above for around $9, coke cans by themselves are worth arund $9.
EXPIRED: 05/05/2021: Chipotle Offer: BOGO with quiz, online or mobile orders only - expires unknown
chipotole doesn't have BOGO offers very often, so whenever there's one, just get it. They are giving out only 50K codes per day. The distribution of these free codes start at 11am CST. Usually they go out in 30 minutes or so, so be ready each day at 11am sharp to grab your codes. Answers for quiz questions are in link above.
EXPIRED: 05/04/2021: Taco Bell Offer: Free Taco - Valid 4th May, 2021 only
https://www.doctorofcredit.com/taco-bell-free-crunchy-taco/
Free crunchy taco offer is back (this time it's taco not nacho). It says beef taco, but you can substitute it with beans to make it vegetarian. At least the online site allows to do it. As always, you can just walk in and get your free taco, or order online or via app.
EXPIRED: 05/01/2021: UMB checking account $300 offer (only valid in select states). => expires May 22, 2021
Look in bank account bonus section for details of the offer: best bank bonus
EXPIRED: 04/26/2021: Walgreens Offer - Get 5.7 oz Crest toothpaste for 50 cents (expiry unknown - will run out of stock fast !!):
https://slickdeals.net/f/14992504-crest-toothpaste-5-7oz-various-0-49-free-store-pickup
There's a coupon for $2, bringing the price to 50 cents. Limit 1 though. If you have offer for $5 in walgreens rewards for spending $20+, use this with almonds offer (see below) + cashew's BOGO offer.
EXPIRED: 04/26/2021: Walgreens Offer - Get 2 colgate toothpaste for free after walgreens rewards (expiry unknown - will run out of stock fast !!):
You have $3 coupon, bringing the price to $5. With this coupon, you get 2 toothpaste for $5 and then $5 rewards, making it kind of free. Don't place online order as Walgreens allows individual stores to cancel online orders based on limits set by manager of that store. So, most of the orders modify your order or cancel your order. Best to go in store and pick these up, as price is valid in store too. If you have an email for $5 rewards on spending $20+, you can combine toothpaste purchase with Almonds purchase below, and get everything for free.
04/26/2021: Walgreens Offer - Buy 36 ounes of Almond for $4 (expiry unknown - will run out of stock fast !!):
With this offer, you get 36 ounces of Almonds for about $4, after applying for $10 rebate, and using BOGO offer on walgreens website. Maximum rebate allowed per consumer is $50, so with people in same household you can do a maximum of $100 in rebate. Costco sells 3 lb bag of Kirkland almonds for $12 or $4/pound. Here you get 36 oz for $4, coming out to $2/lb. This is the cheapest you can get almonds for. Don't place online order as Walgreens allows individual stores to cancel online orders based on limits set by manager of that store. So, most of the orders modify your order or cancel your order. Best to go in store and pick these up, as price is valid in store too.
UPDATE 04/28/2021: Just went to pick these in store, and prices are $.99 instead of $4.59. So, place the order online to save $2.40 for 6 boxes.
UPDATE: 05/01/2021: offer still valid, however stores cancelling or modifying orders by limiting you to 2 or 4 of each type of almonds
EXPIRED: 04/21/2021: Lowes Offer - Buy $200 in Visa GC, get $15 Lowes GC (expires 04/28/2021):
https://www.doctorofcredit.com/lowes-buy-200-visa-giftcard-get-15-lowes-egiftcard-bonus-4-22-4-28/
Similar offer has been offered in the past, but this time it's lucrative, because you can use chase Freedom credit card to get 5% cashback. Chase credit cards have 5% cashback on their freedom cardit cards for "home store" purchases. You can get as many of these as you want, however bonus is limited to 2 per email account. So, effectively for $206 ($200 GC + $6 activation fee), you get $20 in chase points + $15 Lowes eGC, which nets you at least 10% cashback, depending on how much cash redemption value you assign to Lowes GC. NOTE: To get $15 Lowes eGC, you have to go to another website to reddem the offer, after making the purchase in store. Check the link for details.
EXPIRED: 04/16/2021: Krispy Kreme Offer: Free Doughnut - multiple expiry dates
There are 3 offer here:
Really nice offer to get free doughnuts.
EXPIRED: 04/14/2021: Subway Offer - BOGO (expires 06/11/2021): PROMO: FREESUB
https://slickdeals.net/f/14956013-subway-bogo-free-footlong
This offer is back, same as what was offered last few times. It cam right on the day the last offer was supposed to expire. It's buy one, get one free = effectively 2 subway for price of one. Can't beat the price. See below for details. Need to order online or from app. There's another offer on subway website, don't use that, as it's only 50% off of second sub (i.e it's not 100% off as in this deal).
EXPIRED: 04/01/2021: BBVA checking+savings account $250 offer (only valid in select states) => expires Apr 30, 2021:
Look in bank account bonus section for details of the offer: best bank bonus
EXPIRED: 04/01/2021: Scotts Fertilizer Offer at Sam's club - (expires on 04/22/2021):
This sam's club offer beats all the other offers out there for scott's weed and feed fertilizer. It's 40lbs bag is priced at $35, while the cheapest you can get a 42b bag with all the rebates, coupons, cashback etc is about $38 per bag at Ace hardware. So, this iffer at Sam's is much better, you just need to have a membership at Sam's. There are always multiple offers for Sam's, wher you can a yearly membehsip at Sam's for free (i.e Amex/Discover offers that pay you back whatever you pay in membership fees, groupon offers, etc). Also, you can use walmart GC here, so good time to liquidate those.
04/01/2021: Scotts Fertilizer Offer - (expires at different times from 04/2021 to 08/2021):
If you are a home owner with a yard, you know maintaining yards is financially draining. Scott's fertilizers are pretty effective in killing weeds and nourishing your grass, however they are expensive and don't go on sale that often. Ace hardware stores have Scott's fertilizer on sale this month, and with scott's rebate program, you can easily get 20% discount over the sale price. I confirmed with a rep via chat that "Ace hardware" stores are indeed eligible for rebate as they are locally owned stores. These are some of the rebate offers. Don't pay attention to the slickdeals link above, as it doesn't list best possible combo for rebate purposes. There are various lucrative combo possible:
Rebates are all online, so if they come through, it's pretty simple to get the rebate. Rebate forms are not very clear in what's included and what's the rebate per item. Reps were also not able to tell me exactly what quantity of itms need to be bought for rebate, etc. So, it's going to be hit or miss. I've gotten as much info as I could talking to a rep on 1-888-770-9020.
https://www.scottsmiraclegrorebates.com
EXPIRED: 02/28/2021: Subway Offer - BOGO (expires 04/14/2021): PROMO: FREEFOOTLONG
https://slickdeals.net/f/14863126-subway-restaurant-buy-one-footlong-sub-get-one-footlong-sub-free
This offer is back, same as what was offered last few times. It's byu one, get one free = effectively 2 subway for price of one. Can't beat the price. See below for details. Need to order online or from app.
EXPIRED: 02/09/2021: US Bank Checking account $400 offer => expires Mar 31, 2021
Look in bank account bonus section for details of the offer: best bank bonus
Thermodynamic: Thermodynamics simply describes the movement of heat. It deals with heat related motion or other effects. Thermodynamics is derived from thermo, meaning heat, and dynamics, (literally “power”), and is used to describe the movement or change of a process due to heat flow. All below material is relevant only for thermal related energy or work.
NOTE: I've included Thermodynamics as part of Chemistry as that is where it's grouped under in most courses, although it could as well be part of Physics, as it invloves Energy, work, etc.
Any object has observable properties as Temperature, Pressure and Volume. These are macroscopic properties observed at object level, but all these objects are made of microscopic components called atoms, which combine to form molecules. Each of these molecules has a distinct state such as position and velocity, which ultimately decides the microstate of each molecule. Microstate of all these molecules combined define the macrostate of the system/object that we observe.
Entropy: It is the measure of how disorganized and random a system is.
Entropy is defined as all possible microstates that the system can occupy. If each state "i" has a probability pi of being occupied, then entrpoy (S) is =>
S = -kb Σ pi log (pi) => Here kb=boltzmann constant = 1.38x10^-23 J/K. So, unit of S is also J/K. Kb provides conversion from Temp to Energy and represents the energy of a particle per unit temperature. So, a particle at 0K has 0 energy but one at 100K has 1.38*10^-21J (multiplying Kb by 100)
If a system has Ω number of possible microstates, and each microstate has equal probability of happening, then S = -kb * Ω * 1/ Ω * log (1/ Ω) => S= kb*log( Ω). This is true for an isolated system in equilibrium. In thermodynamics, such a system is one in which the volume, number of molecules, and internal energy are fixed.
In other words, entropy measures the disorder or uncertainty about a system, i.e billions of different possible microstates that the system can have, can give rise to uncertainty as to what state the system is in now. If there are 50 molecules of water, and each molecule of water can be in 10 different states, then total number of possible states is 10^50 (since each molecule can be in any of 10 states, and there are 50 molecules, so simple probability says it is 10 multiplied 50 times). So, entropy is kb*log( Ω) = kb*log(10^50).
NOTE that entropy is a measure of a system's thermal energy per unit temperature that is unavailable for doing useful work. Every system has internal thermal energy in it, that keeps atoms vibrating. As we cool things, things change from gas to liquid (less vibration), then to solid (even less vibration), then start getting into more perfect lattice. If we go to very low temperature close to 0K, we will get lattice structure where there is no vibration, and each atom of lattice is exactly the same way as any other atom. There is no variation or disorder in this lattice structure. It behaves like a perfect crystal, one in which the internal lattice structure extends uninterrupted in all directions. Every lattice element of the structure is in its proper place, whether it is a single atom or a molecular grouping. Possible number of micro states is just 1 which is the ground state (since each atom has only 1 state (no vibration), so irrespective of number of atoms, there can be only one state for system, as all atoms will have that 1 state). In this case entropy = kb * (log 1) = 0.
So, at absolute zero temperature (0 Kelvin or -273.15C), entropy of a system should ideally be 0 (i.e only single ground state possible for all atoms). However, in reality perfect crystal structure is not achieved even at 0K. There are other micro states besides the ground state. In other words, the system is at lowest internal energy state (least vibration), but not 0. There is still vibrational motion in particles, which cannot be removed. Perfect crystals never occur in practice; imperfections, and even entire amorphous material inclusions, can and do get "frozen in" at low temperatures, so transitions to more stable states do not occur (even though there may be multiple micro states, but we may just see 1 micro state). Correct form of 3rd law of thermodynamics (mentioned below) is that entropy approaches 0 as temperature goes to 0. So, Entropy at 0K is some finite residual value, but for convenience, we take entropy at 0K to be zero, for reference.
Three Laws of Thermodynamics:
Just like we have Newton's laws for motion, we have 3 separate laws for thermodynamics (as no other laws explain thermal observations. Newton's laws are limited to mechanics). There is also a “Zeroth”L aw that states, in a rather complicated way, that no heat will flow between two objects that are at the same temperature. This seems so obvious that this law is generally ignored, in common practice.
First Law- Energy cannot be created or destroyed, but can change form, and location. For instance, burning wood changes the internal energy in the wood into heat and light energy.
Second Law- The Second Law is the most understandable and useful in real world applications, and makes heating, air conditioning, and refrigeration possible. It is expressed in many different forms, but they all amount to the same thing. Easiest and most common defn is that energy must flow from a higher state to a lower state. That is, heat must always flow from the warmer object to a cooler object and not from the cooler object to the warmer object, unless energy in some form is supplied to reverse the direction of heat flow. Another definition is: "Not all heat energy can be converted into work in a cyclic process, i.e Work can create heat, but not all heat can be converted back to work.
The second law basically is about Entropy and may be formulated by the observation that the entropy of isolated systems left to spontaneous evolution cannot decrease, as they always arrive at a state of Thermodynamic Equilibrium where the entropy is highest at the given internal energy. An increase in the combined entropy of system and surroundings accounts for the irreversibility of natural processes, often referred to in the concept of the arrow of time. 2nd Law of Thermodynamics is also sometimes called as "Law of Entropy", which states that Entropy in Universe is always increasing.
The Second Law holds in our everyday visible world, but on the subatomic level the law is constantly violated, but statistically the law holds true.
Third Law- As a system approaches Absolute Zero, the entropy of the system approaches a minimum value. Absolute Zero cannot be attained in a real system, it is only a theoretical limit. We saw this above.
Heat Transfer:
Heat can move in three ways: conduction, convection, and radiation.
Conduction is the easiest and most familiar to anyone who has burned themselves on a stove or a hot pot. It is the direct transfer of heat from one object to another, when they are in contact.
Convection is based on the movement of a fluid to transfer heat from one object or area to another. Weather is a convective process; hot air and warm water move from the tropics toward the poles. Here air or water was used as the medium for transfer.
Radiation is heat transferred directly from a source to an object without using a medium like air or water. Heat radiated from the sun will melt snow on the road, even on a cold day. The radiant energy warms the road surface without directly warming the air.
In the real world, the transfer of heat involves a mixture of all three methods, with the possible exception of outer space.
Fermi:
This defn not correct => The Fermi level for electrons of a body is the thermodynamic work required to add one electron to the body. It's the same amount of work to remove one electron from the body. It is a thermodynamic quantity usually denoted by µ or Ef. It's unit is Joules, as it is energy level, not potential level.
We saw above that each electron in a crystal lattice is in an energy band. However there is a probability distribution that says how many of these electrons will be in which energy level at a given temperature.
The Fermi–Dirac distribution, f ( ϵ ), gives the probability that (at thermodynamic equilibrium) a state having energy ϵ is occupied by an electron:
f ( ϵ ) = 1 / [e^{(ϵ − μ)/kT} + 1]
Fermi level can be considered to be a hypothetical energy level of an electron, such that at thermodynamic equilibrium this energy level would have a 50% probability of being occupied at any given time. At 0K, since all thermodynamic motion ceases, we would expect that electrons would be frozen, i.e at lowest energy level E0. From above eqn we see that at 0K, all Energy levels below Ef have 100% prob of being occupied, while those above Ef have 0% prob. As is expected at 0K, all these energy states are occupied with 100% certainty, implying only 1 micro state possible (i.e lower N energy states occupied, while upper energy states not occupied. No other combination of energy states possible).
The Fermi level is any energy level having the probability that it is exactly half filled with electrons. Levels of lower energy than the Fermi level tend to be entirely filled with electrons, whereas energy levels higher than the Fermi tend to be empty. Enrgy bands above Ef are called conduction band, while those below Ef are called valence band.
For conducting metals, both conduction and valence band are on each side of Ef right next to it, meaning just little bit of extra energy is needed for these electrons to conduct. Even with no extra energy applied, a lot of thermally active electrons are in conduction band. This causes the electrons to move freely resulting in high conductivity. For insulators, these conduction and valence are further separated out from each other, with Ef in b/w. This means a lot of extra energy is needed for these electrons to conduct. There is a band gap b/w cond and val band, of the order of 10ev. Almost no electrons are in conduction band, resulting in no conductivity. Semiconductors also have these bandgap, are lot smaller bandgap of 1ev. So, conduction band is very lightly populated with thermally active electrons resulting in low conductivity. Apart from thermal agitation, providing light energy is the other way to move electrons from valence band to conduction band.
NOTE: Fermi level moves around with external voltage applied, so Fermi level is defined with 0 external voltage. Fermi level moves up by "X eV", when "X Volts" applied to the material. So, alternatively, when we say that a conductor is at "X Volts", all electrons have gained an additional "X eV" of energy, so all of the energy band has shifted up by "X eV", so Fermi level has also moved up by "X eV". So, Fermi level can be known by just dividing voltage of material by "e", if we assign fermi level of 0, for electrical ground (i.e 0 external voltage).
Work function (W)
As we move higher up in energy band (in conduction band), electrons become more free to move around, but still within the solid material. If we go much higher than conduction band region, then electron may finally beak free from the surface of solid. We call this energy level Work function. It's defined as minimum thermodynamic work (or energy) needed to remove an electron from a solid to a point in the vacuum immediately outside the solid surface. Here "immediately" means that the final electron position is far from the surface on the atomic scale, but still too close to the solid to be influenced by ambient electric fields in the vacuum. The work function is not a characteristic of a bulk material, but rather a property of the surface of the material (depending on crystal face and contamination). Work function of most of the metals is around 4eV. Silicon W=4.7eV
W = -eø - Ef (e=charge of electron, ø = electrostatic potential in the vacuum nearby the surface, so -eø represents the energy of electron near the surface)
If we charged a material to V volts, then V=-Ef/e. Rearranging above eqn, ø = -Ef/e - W/e = V - W/e. So, potential near surface of any material in vacuum is less than the potential applied by an amount equal to Work function potential (work function divided by e). This means that if 2 conductors are kept at same potential by shorting to each other, but if their work function are different, then their surface potential will be different. So, there will be an electric field in vacuum going from surface of 1 metal to other metal. This is used to get electrons flowing in vacuum tube filaments or in electron guns.
Work function is very important in solid state physics, as work function of different material control how electrons flow when different materials are put in contact.
It is also important in photo electric emission, where it determines the minimum photon energy required to liberate an electron from a substance. Energy beyond fermi level gets the electron right on the surface of material ready to escape. So, light of frequecy f has energy=hf, which when exceeds workfunction of material will liberate an electron from it.
