Question

Define the term "potential difference" between two points in an electric circuit carrying current. Name and define its S.I. unit. Also express it in terms of S.I. unit of work and charge.

Answer 1

Potential Difference

Definition:

Potential difference (V) is the work (W) required to move a unit positive charge (q) between two points in an electric circuit.

Mathematically: \[ V = \frac{W}{q} \]

S.I. Unit of Potential Difference:

The S.I. unit is the Volt (V).

Definition of 1 Volt:

One volt represents the potential difference when 1 joule of work moves a 1 coulomb charge: \[ 1 \text{ V} = \frac{1 \text{ J}}{1 \text{ C}} = 1 \text{ J/C} \]

Expression in Terms of S.I. Units:

Since:

• Work (W) is measured in joules (J)
• Charge (q) is measured in coulombs (C)

Therefore: \[ \text{Volt (V)} = \frac{\text{Joule (J)}}{\text{Coulomb (C)}} \]

Summary Points:

• Definition: Work done per unit charge
• Mathematical Form: \( \Delta V = \frac{W}{q} \)
• S.I. Unit: Volt (V)
• Dimensional Formula: [ML²T⁻³I⁻¹]
• Base Unit Equivalence: 1 V = 1 J/C