Physics Review Question

Unit: Electricity and Magnetism
Year: 1997 Question#: 32
Question: An electric dryer consumes 6.0 * 106 joules of energy when operating at 220 volts for 30. minutes (1800 seconds). During operation, the dryer draws a current of approximately

(1 ) 10. A
(2 ) 15 A
(3 ) 20. A
(4 ) 25 A

What is this question really asking?




Explanation by: Ajemo H

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Answer 1
10. A

INCORRECT

The equation for current is W=VIt. Where W=energy, V=voltage, I=current, and t=time.
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Answer 2
15 A

CORRECT

The equation for current is W=VIt. Where W=energy, V=voltage, I=current, and t=time. If you plug 6000000J in for W, 220v in for V, and 1800s for t. You can solve for current (I). The number you get is 15.15A. since all of the other numbers have at least two significant figures, you have to use an answer of 15 A. return to top



























Answer 3
20. A

INCORRECT

The equation for current is W=VIt. Where W=energy, V=voltage, I=current, and t=time. return to top


























Answer 4
25 A

INCORRECT

The equation for current is W=VIt. Where W=energy, V=voltage, I=current, and t=time. return to top


























What's this question really asking?

This question is asking if you know how to use the electrical work formula in the appropriate places. The key is to recognize that work and energy are the same thing. So when you calculate the work done you are also finding the energy used. It also asks if you know your sientific notation. return to top

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