EMF Formula

EMF Formula

The electromagnetic force, sometimes known colloquially as emf, is an electrical action created by a non-electrical source. Many gadgets generate this force by transforming various types of energy into electrical energy. These might include loudspeakers, sensors, microphones, thermometers, and so forth. Batteries, for example, are engaged in chemical energy conversion. The role of emf is clearly visible in the instance of a closed-loop of conductors. If an electron goes once around the loop, it experiences the electromagnetic function performed on it. This is how emf contributes to electromagnetic induction. Michael Faraday, an English scientist, developed the notion of emf for the first time in 1830. Volts are the SI unit for measuring emf. It is represented by the symbol ε.

What is EMF?

The electromotive force is defined as the potential difference between the battery’s terminals when no current flows through it. This can not appear to make a difference, but every battery has internal resistance. The EMF Formula  functions similarly to typical resistance in a circuit, except it occurs within the battery itself.

When there is no current flowing through the cell, this internal resistance has no effect since there is no current to slow down. In this sense, the EMF can be defined as the highest potential difference between the terminals in an imagined condition.

The electromotive force, or the EMF Formula, is the amount of energy delivered by a battery or cell per coulomb (Q) of charge travelling through it. When no current flows through the circuit, the emf equals the V (potential difference) between the cell terminals.

Difference between EMF and Potential Difference?

The quantity of energy turned into electrical energy per coulomb of charge is referred to as EMF. In contrast, the potential difference is the amount of electrical energy transferred into other forms of energy per coulomb of charge. Sources of emf include cells, solar cells, batteries, generators, thermocouples, dynamos, and so on.

Formula for Calculating the EMF

Students know that charges circulate in an electric circuit; but, for the charges to move in a specific electric circuit, they must apply an external force to it. They argue that an external electric source, such as a battery, utilises such force to accelerate the charges, which is known as the electromotive force. Despite its name, it is a potential difference rather than a type of force. The EMF Formula  is a type of potential difference that is commonly represented by the symbol.

The EMF Formula is calculated using two primary equations. The basic definition is the number of joules of energy picked up by each coulomb of charge as it passes through the cell.

The EMF Formula = EQ

Ε is noted as electromotive force

E is denoted energy in the circuit

Q is cited as the Charge of the circuit.

Solved Examples for EMF Formula

Example: What is the terminal potential difference of a cell connected to a 12-ohm load, if the cell’s EMF is  2 Volts and its internal resistance is 4 ohms?



EMF (e) = 2 Volts

External resistance (R) = 12 ohms

Internal resistance (r) = 4 ohms

As per Ohm’s law, I = V/R

The total resistance (R) = External resistance + Internal resistance = 12 + 4 = 16 ohms

So, I = 2/16 = 0.125 Ampere

Using the formula, e = V + Ir

2 = V + (0.125)4

Solving for V, we get V =2 – 0.5

Hence, the terminal potential difference, V = 1.5 Volts

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Electric Field Formula Poynting Vector Formula
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Ohms Law Formula Amperes Law Formula
Refractive Index Formula Horsepower Formula
Wavelength Formula Lattice Energy Formula
Stress Formula Length Contraction Formula

FAQs (Frequently Asked Questions)

1. What is the formula for EMF?

The formula for EMF (e) is –

e = E/Q

where E is energy, and Q is charge. It can also be written as e = IR + Ir or, e = V + Ir.

2. How to calculate the terminal potential difference of a cell?

A cell’s terminal potential difference may be determined using the formula e = V + Ir, where e is the electromotive force, I is the current, r is the cell’s internal resistance, and V is the terminal potential difference.

3. What is the difference between EMF and Potential Difference?

EMF is the amount of energy (of any kind) converted into electrical energy per coulomb of charge, whereas potential difference is the amount of electrical energy converted into other types of energy per coulomb of charge.