Class 10 > Unit # 15: Current Electricity > Electric Potential and EMF

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Potential Difference and Electromotive Force (EMF)

Q.2 Describe the terms potential difference and electromotive force (EMF).

Potential Difference

"When a charge moves through a potential difference, electrical work is done and energy is transferred. Potential difference is the difference in the amount of potential energy that charge carriers have between two points in an electric field."

Mathematical Equation

If work $W$ is done in moving a charge $Q$ between two points, the potential difference $V$ is given by:

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

Unit

Potential difference is measured in volts ($\text{V}$):

$1\text{ V} = 1\text{ Joule} / 1\text{ Coulomb} = 1\text{ J/C}$

Fig: Potential difference ($V$) driving charge through a conductor between two points.

Electromotive Force (EMF)

"The amount of energy required to move a unit charge from the lower potential terminal to the higher potential terminal inside a source (like a battery) is called Electromotive Force (EMF)."

Mathematical Equation

$\text{EMF } (\mathcal{E}) = \frac{\text{Energy Supplied } (W)}{\text{Unit Charge } (q)}$

Units

1. SI Unit: The SI unit of EMF is the volt ($\text{V}$) (equivalent to joules per coulomb).
2. CGS System: In the centimeter-gram-second system, the unit of EMF is the statvolt (or one erg per electrostatic unit of charge).

Fig: Energy supply and charge transfer from lower to higher potential inside a voltage source (EMF).

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