Question

The potential difference across a resistor increases by a factor of 2. How does the current change? (Ohm's law: V = IR) A. It decreases by a factor of 2. B. It increases by a factor of 4. C. It increases by a factor of 2. D. It decreases by a factor of 4.

Answer 1

The current increases by a factor of 2.

Answer 2

The answer is C.

The question says the potential difference is what is changing, which means we're solving for V.

It tells us that potential difference increases by a factor of two, which just means V doubles.

With this info, we can pick some numbers, plug it into Ohms law and see what happens.

Here's an example where I just picked random numbers that are easy to work with:

V=I*R
10=I*5
I=2
Lets increase the potential difference (V) by a factor of two and see what happens to current:
V=I*R
20=I*5 (all I've done is double the potential difference from 10 to 20)
I=4

When we increase V by a factor of 2, I increases by a factor of 2. We went from I=2 to I=4.
We can increase V by factor of 2 again and see:
V=I*R
40=I*5
I=8

Okay, current just increased by a factor of 2 again when we increased the potential difference by a factor of 2.

It's always good to check work with alternate numbers, so here's one more set:
V=I*R
16=I*4
(remember, we know we're solving for V, so I'm just plugging in random numbers for I and R)
I=4
Increase V by factor of 2:
32=I*4
I=8

So, when we increase V (the potential difference) by a factor of 2, I (current) always increases by a factor of 2 as well.

Hope this helps!