One volt is equal to:
A. 1 Joule
B. 1 Newton/Coulomb
C. 1 Joule/Coulomb
D. 1 Coulomb/Newton

Hint: In this case we should check for any formally defined equation related to it. This will give us an idea of the unit or the ratio of units involved.

Complete step by step answer:

We can define 1 volt as “It is the potential difference between two points that will impart one joule of energy per coulomb of charge that passes through it.” Which can be expressed as
$\text{1Volt}=\dfrac{\text{1joule}}{\text{coulomb}}$
So, we know that the unit of energy is joules and for charge is coulomb in the SI unit system.
So the answer to the question is option (C) 1 Joule/Coulomb.

Additional Information:

Volt can also be expressed as:

From Ohm’s law we can express volt as amperes times ohms, where ampere is the unit for current and ohms for resistance.
From Faraday’s law of induction, we can write volt webers per second where weber is the unit for magnetic flux and second for time.
From the equation of power P=VI we can write volt as watts per ampere where watt is the unit of power.

Note: If we consider other options in the question like option (A), which is joules which is a unit for energy or work and not of volt.
If we consider the option (B), which is 1 Newton/Coulomb, by looking at the units involved like newton for force and coulomb for charge we can relate it to an electric field which has the same unit. So it does not signify volt.

Moving onto option (D), it is just the reciprocal of option (B), so it is not the answer.