Which of the following is a correct unit of potential difference (voltage)?
A amp per ohm
B coulomb per joule
C joule per second
D newton per coulomb
E watt per amp

Answer:

7) E

A – Wrong
Voltage = current x resistance = amp x ohm. Hence amp/ohm is wrong.

B – Wrong 
We cannot prove voltage = coulomb per joule

C – Wrong 
joule/second is the unit of power

D – Wrong
We cannot prove voltage = newton per coulomb

E – Wrong 
We know power = voltage x current. voltage = power/current = watt/amp = watt per amp