Physics repost

A current of 5.0 A flows for 20.0 minutes through a bulb and delivers 15000 J of electric energy to the bulb. What is the potential difference across the bulb?

A)2.5 V
B)4 V
C)100 V
D)100 V (book typo)

I was told to do this: energy= V*I*time in seconds solve for v. I don't really understand that so I did this: 5*1200= 3000 and 15000/3000= 2.5 so the answer is A

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1. You did the math wrong twice, yet you ended up with the right answer, (A). You were just lucky.

15,000/3000 = 5 (not 2.5)

5A*1200s = 6000 Coulombs (not 3000)
Energy/Coulombs = voltage
Your method is an acceptable way to do the problem, and gives the right answer the numbers are done right.

Here is yet another way to do it

The power is P = 15000J/1200s = 12.5 W

12.5 = V*I
V = 12.5/5 = 2.5 V

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posted by drwls
2. a small error in what I typed. I meant 5*1200= 6000 not 3000 duh and then 15000/6000 = 2.5 THATS what I did.

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posted by Jon

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