What is difference between voltage and emf?

Answer 1

An electromotive force (e.m.f.) is the open-circuit, or no-load, potential difference provided by a source -such as a battery or generator. For a closed circuit, an e.m.f. is the sum of the voltage-drops around any closed loop, including the internal voltage drop of the source.

A potential difference (voltage) can exist across any circuit component. For example, the fact that current is flowing through each of several resistors in a series circuit means that there must be an individual potential difference across each of those resistors (which we also term 'voltage drop').

An electromotive force is the name we give to the open-circuit potential difference provided by a generator, battery, etc. For example, the open circuit potential difference of a battery would be its electromotive force.

So, if we use a series resistive circuit as an example, the battery would provide the electromotive force, while voltage drops would then appear across its internal resistance, and across each of the resistances. The magnitude of the electromotive force is then equal (but acting in the opposite sense) to the sum of the voltage drops, including the internal voltage drop.

Many textbooks use the symbol, E, to represent an electromotive force, and V to represent potential difference. So, Kirchhoff's Voltage Law, for example, will often be seen written as: E = V1 + V2 + V3 + etc.

Answer 2

1) EMF of a battery is the amount of electrical energy required to move a unit positive charge from the negative to the positive terminal of the battery when the battery is open circuited, whereas, potential difference across the terminals of a battery is the energy required for the same process but when the battery is in use, that is, current is flowing through it.

2)Since when current flows through the battery, some amount of energy is lost in overcoming the internal resistance of the battery, the difference in energy between the two terminals of the battery is somewhat less that it is when current does not flow. Hence, EMF is always greater than potential difference and is the sum of potential difference and the energy lost due to internal resistance.

3)While talking about a circuit, EMF is an independent variable and is the voltage that causes current( i=v/r ) but potential difference is a dependent variable and is the voltage between two points of the circuit as an effect of a current ( v=i*r ).

4) EMF is constant and independent of the resistance of circuit whereas potential difference varies.

5)The source of EMF is that part of a circuit where electrical energy is created from any other form of energy,but potential difference is said to exist in that part of the circuit where electrical energy is converted in to any other form of energy.

Answer 3

EMF stands for Electromotive force. EMF is measured in units of volts.