# Relationship between potential difference and emf

### Difference Between Electromotive Force & Potential Difference with Comparison Chart - Circuit Globe

Demonstration Opening up discussion of the difference between potential difference (p.d.) and electromotive force (e.m.f.). Apparatus and materials volt . The distinction between emf and potential difference is often glossed to emf than what I've outlined here and the Wikipedia article (and links. EMF and Potential DifferenceIn any circuit there are components that put energy in to the circuit and components that take energy out. From now on, we will say.

Example — Consider a circuit shown in the figure below.

A 12 volt supply applies across the resistance of the circuit. The potential difference between any two points, says A and B, is the energy used by one coulomb of charge in moving from one point A to the other B.

Definition of Electromotive force The electromotive force is the total voltage induce by the source. In other words, it is the amount of energy supplied by the source to each coulomb of charge.

The emf is the maximum voltage that can be attained by the circuit. Naturally, it is generated when the fluctuation occurs in the magnetic field.

The emf is expressed by the formula shown below The electromotive force is the type of energy which forces a unit positive charge to move from the positive to the negative terminal of the source. It separates the two charges from each other. A battery has an EMF of 12V ; it means that the battery supplies 12 joules of energy to each coulomb of charge.

The charge is travel from the positive terminal to negative terminal through an external circuit; it gives a whole of the energy originally supplied by the battery. The electromotive force is the measure of energy that it gives to each coulomb of charge, whereas the potential difference is the amount of energy used by the one coulomb of charge.

## Potential difference and e.m.f.

The electromotive force does not depend on the internal resistance of the circuit whereas the potential difference is directly proportional to the resistance of the circuit.

Ask for a new interpretation e. The voltmeter is connected to terminals on the outside of the box. More lamps can be added in parallel to increase the current and so reduce the terminal potential difference. Teaching notes 1 Encourage students to think, as follows: Potential differences are electrical pressure differences between the ends of some part of a circuit where electrical energy is transferred to a lamp or other component.

### Electromotive Force and Internal Resistance

Voltmeters are devices to measure energy transfer for each coulomb passing through that part of the circuit. What happens if there is only the battery and no outside circuit?

The voltmeter gives a reading and, if the voltmeter is a good one very high resistancethen it may read slightly higher than when the battery is connected across a circuit. When the battery is disconnected from the circuit the voltmeter is reading the energy transfer from chemical to electrical in the cell.

We call that the e. It is the ' uphill push ' which the battery can give to a coulomb before it slides downhill in the rest of the circuit. Some energy is needed to transfer the coulomb through the battery.