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Question 24 of 36

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SAT Subject Test

The figure presents an electrical circuit with a battery in series with a resistor. The battery is on the left side of the circuit and is labeled with the emf symbol (the Greek letter epsilon). The resistor is on the right side of the circuit and is labeled R. On the top side of the circuit there is an arrow pointing toward the right that is labeled I.

A single resistor R is connected to a battery as shown above. The current is I and the power dissipated as heat is P. The circuit is changed by doubling the emf epsilon of the battery while R is kept constant.

After the change, the current is

Select an Answer

I over 4

Correct Answer: 
No

I over 2

Correct Answer: 
No

I

Correct Answer: 
No

2 I

Correct Answer: 
Yes

4 I

Correct Answer: 
No

The correct answer is 2 I. In this series circuit with just one resistor, the emf across the battery is equal to the voltage V across the resistor, so if the emf is doubled so is V. The current I in the resistor is given by Ohm’s law, I invisible times equals V divided by R, so if V is doubled while the resistance R remains constant, then I is also doubled.

Question Difficulty: 
medium