# Electric field and coffee maker

1) A coffe maker which draws 13.5A of current has been left on for 10 min. what is the net number of electrons that have passed thru the coffe maker.

[del]Q = I * [del]T = 13.5(600) = 8.1x10^3

I got this wrong, what happened?

2) a battery is rated 12V and 160Amp-hours. How much energy does the battery store?

12V * 160 = 1.9kJ

I got this wrong, can anyone gimme the correct formula(s) to plug in and solve

Homework Helper
10 minutes is 600 seconds so your answer appears to be assuming that one ampere is "one electron per second". Where did you get that idea.

I suspect that your textbook has definitions of "ampere" and "volt". I recommend that you review them.

Originally posted by HallsofIvy
10 minutes is 600 seconds so your answer appears to be assuming that one ampere is "one electron per second". Where did you get that idea.

I suspect that your textbook has definitions of "ampere" and "volt". I recommend that you review them.

No it doesn't Ivy! It gives me the definition but no examples on solving these questions. I saw that 1A = 1c/s but confused on its formula. I assumed youmultiply but i donno. Can you please point me in the right direction.

Staff Emeritus
Gold Member
Does the book have the amount of electrons per coulomb?

Staff Emeritus
Gold Member
HallsofIvy: I suspect that your textbook has definitions of "ampere" and "volt". I recommend that you review them.

Dx: No it doesn't Ivy!

Of course it does. Any textbook worth its salt would have it.

1 Ampere is 1C/s, right?
And 1 electron has a charge of 1.6x10-19C, right?

From that you should be able to figure out how many electrons per second correspond to 1 Amp.

Homework Helper
DX, you have a problem with reading your book. You answer firmly that your book does NOT have a definition of "ampere" and then state
"I saw that 1A = 1c/s but confused on its formula." That IS a definition of ampere! It says that one ampere means one coulomb of electricity per second. Now you need to look up how many electrons there are in a coulomb. Hint: use the index of your book.

By the way I asked "where did you get the idea that one ampere mean one electron per second" and you answered that you didn't know the definition. You HAVE to know the definitions of the words in problems before you can do the problems! Grabbing numbers out the problem at random and combining them in random ways is not a good way to solve problems.

Originally posted by HallsofIvy
DX, you have a problem with reading your book. You answer firmly that your book does NOT have a definition of "ampere" and then state
"I saw that 1A = 1c/s but confused on its formula." That IS a definition of ampere! It says that one ampere means one coulomb of electricity per second. Now you need to look up how many electrons there are in a coulomb. Hint: use the index of your book.

By the way I asked "where did you get the idea that one ampere mean one electron per second" and you answered that you didn't know the definition. You HAVE to know the definitions of the words in problems before you can do the problems! Grabbing numbers out the problem at random and combining them in random ways is not a good way to solve problems.

Yes, sometimes I overlook things in the book, it happens. So what, sue me! I made a mistake and so did you by making this personal. Don't worry about me overlooking a simple definition and just remember what goes around comes around mr. index.
Dx

And if anyone else feels the same way, you can re-read my post. Man that really offends me "Ask for help and all you get is sarcassim. I didn't comprehend the fact. I asked for help set-up my problem which is what I was asked for help with not a definition." To me, your response didn't help me as i was asking so i was honest when i replied to your post.

Anyways...h20 under the bridge were cool Ivy!
Dx

Staff Emeritus
Gold Member
Originally posted by Dx
Yes, sometimes I overlook things in the book, it happens. So what, sue me! I made a mistake and so did you by making this personal. Don't worry about me overlooking a simple definition and just remember what goes around comes around mr. index.
Dx

Chill out, Dx. Ivy is right: You don't seem to like to study. You could easily answer most of the questions you post here by reading (not skimming!) your textbook. Asking questions that are answered in the inside cover of any textbook (eg: "What's the charge on 1kg of protons?") gives the impression that you are lazy.

And if anyone else feels the same way, you can re-read my post. Man that really offends me "Ask for help and all you get is sarcassim.

That is just not true. You have posted many threads here, and no one has responed with sarcasm. It's called constructive criticism. You need to learn the difference.

Homework Helper
Not sarcasm (by the way, you spelled it wrong just facts: to do mathematics or physics you have to be PRECISE. I'm not going to sue you- you are the one that will suffer if you do not read your textbooks: 1) CAREFULLY 2) REPEATEDLY 3) WITH PAPER AND PENCIL AT HAND.

My comment about knowing the definitions was the best help I can give you: it is not enough to have a general idea what a word means. Definitions in mathematics and physics (and other studies) are WORKING definitions: you use the specific words in the definitions to work problems.

Now: How many electrons are there in a coulomb?

I want to publiclly apologize to HallsofIvy for my rude remarks. Your %100 correct Ivy, I am taking a few days off to chill out. I will be around but just reading not posting. Let's just say yesterday wasn't the greayesy of my days, ok. Anyways, You, Tom and pretty much everyone else has been a big help and even though I am getting close to the end of my Physics 2 class I want to say thanks for everything and God help me! Kidding! Seriouly, Thanks!

Tell you what, dinner on me someday. You never know when you might be setting next to ol dx on a plane or biking the mountains of Spain. YES!

PEACE OUT!
dx