What is the formula for EMF

 Electromotive Force

What is the formula for EMF?

Electromotive force (EMF) is the energy per unit charge that is supplied by a source of electrical energy such as a battery or a generator. The SI unit of EMF is the volt (V).

The formula for EMF is:

where:

e is the EMF (in volts)
I is the current (in amps)
R is the load resistance (in ohms)
r is the internal resistance of the source (in ohms)

The term IR represents the potential difference across the load resistance, and the term Ir represents the potential difference across the internal resistance of the source.

In the case of a battery, the internal resistance is due to the resistance of the electrolyte and the electrodes. The internal resistance of a battery decreases as the battery ages.

The EMF of a battery is equal to the potential difference across the terminals of the battery when there is no current flowing.

Examples

Suppose a battery has an EMF of 12 V, a load resistance of 2 ohms, and an internal resistance of 0.5 ohms. The potential difference across the load resistance will be 9.6 V, and the potential difference across the internal resistance will be 2.4 V.
Suppose a generator has an EMF of 240 V and a load resistance of 10 ohms and an internal resistance of 0.5 ohms. The potential difference across the load resistance will be 229 V, and the potential difference across the internal resistance will be 11 V.

Applications

The formula for EMF is used in many applications, including:

• Calculating the potential difference across a load resistance
• Calculating the internal resistance of a source
• Calculating the efficiency of a source
• Designing circuits

I hope this note helps! Let me know if you have any other questions.

FAQs about the formula for EMF:

What is EMF?

EMF stands for electromotive force. It is the energy per unit charge that is supplied by a source of electrical energy. The SI unit of EMF is the volt (V).

What is the formula for EMF?

The formula for EMF is:

 

e = IR + Ir

where:e is the EMF (in volts)
I is the current (in amps)
R is the load resistance (in ohms)
r is the internal resistance of the source (in ohms)

What is the difference between EMF and terminal voltage?

EMF is the maximum potential difference that a source can provide. Terminal voltage is the actual potential difference that is available across the terminals of the source when a load is connected. The terminal voltage is always less than the EMF due to the internal resistance of the source.

What are the applications of the formula for EMF?

The formula for EMF is used in many applications, including:

• Calculating the potential difference across a load resistance
• Calculating the internal resistance of a source
• Calculating the efficiency of a source
• Designing circuits

What are some common mistakes people make when using the formula for EMF?

Some common mistakes people make when using the formula for EMF include:

• Forgetting to include the internal resistance of the source
• Using the formula for terminal voltage instead of EMF
• Not understanding the difference between EMF and potential difference

I hope this helps! Let me know if you have any other questions.