Question

A circuit consists of a battery and two resistors connected in parallel. If the resistance in both resistors is doubled, and the current is kept constant, how does the voltage change?

A) The voltage is quartered
B) The voltage is halved
C) The voltage remains the same
D) The voltage is doubled

Answer 1

The answer is D. because if both resistors are doubled and the current is costant then it would double the voltage.

Answer 2

Let initial resistances be R and R
effective resistance = R*R/R+R = R/2

When they are doubled, Effective resistance = 2R*2R/2R+2R = R

So effective resistance is doubled.
We know; V = IR. R is doubled and I is constant. Thus V is doubled.
Answer is D.

Hope it helps!