Question

What is the SI unit of electrical potential?
A. ampere
B. volt
C. volt.m
D. coulomb

Answer 1

Hint: Recall the formula for the electrical potential i.e., $$V={\displaystyle \frac{W}{Q}}$$ thereafter by putting units of the quantities in the right hand side, you will be able to find out the required S.I. unit of electric potential.

Complete step by step answer:
Electric potential is the amount of work needed to move a unit charge from a reference point to a specific point against an electric field.

Generally, the reference point is the earth, although any point beyond the influence of the electric field charge can be used.

Mathematically, the electric potential is given by,

$$V={\displaystyle \frac{W}{Q}}$$

On writing units, we have

$${\displaystyle \frac{\text{joule}}{\text{coulomb}}}$$

Which is known as volt i.e.,

$$\text{1 volt = 1}{\displaystyle \frac{\text{joule}}{\text{coulomb}}}$$

Hence, the correct option is B, i.e., volt.

Additional Information:
One Volt is defined as energy consumption of one joule per electric charge of one coulomb i.e.,

1 V = 1 joule/coulomb

Or it can be also be defined as,

One volt is equal to current of 1 ampere times the resistance of 1 ohm i.e.,

1 V = 1 Ampere×1 Ω

A difference in electric potential gives rise to an electric field. The electric field is the force per unit charge acting on an imaginary test charge at any location in space.

Note: Students should memorize the formula for various basic physical quantities, so that they can easily find out the correct unit of these quantities. Here ampere is the unit of electric current so option A is incorrect and coulomb is the unit of electric charge so option D is also incorrect, while option B i.e. volt.m is given here just to create confusion, so student need not to confuse and mark the correct answer i.e. volt.