If the voltage impressed across a circuit is held constant while the resistance doubles, what change occurs in the current?

The current halves

Explanation:

The relationship between voltage, current and resistance in a circuit is given by Ohm's law:

where

V is the voltage

R is the resistance

I is the current

We can rewrite the formula as

we see that I is directly proportional to V and inversely proportional to R.  In this problem, V is held constant while R is doubled:

so, the new current in the circuit will be

So, the current halves.

at positions a, g kinetic energy is maximum.

at position d, potential energy is maximum.