Question

how does the current in a circuit change if the voltage is doubled and the resistance remain unchanged?
no change.
triples.
doubles
reduced by half.

Explanation:

Step1: Recall Ohm's Law

Ohm's Law is $I = \frac{V}{R}$, where $I$ is current, $V$ is voltage and $R$ is resistance.

Step2: Analyze the change

Let the initial voltage be $V_1$ and current be $I_1=\frac{V_1}{R}$. The new voltage $V_2 = 2V_1$ and resistance $R_2=R_1 = R$. Then the new current $I_2=\frac{V_2}{R_2}=\frac{2V_1}{R}=2\times\frac{V_1}{R}=2I_1$.

Answer:

doubles