Formulae for EMF

EMF, or electromotive force, is the electric potential difference between two points in a circuit that drives the flow of electric current. It is measured in volts (V). In order to understand the formulae for EMF, it is important to first understand the concepts of electric current, Ohm's Law, and the drift of electrons.

Electric Current:
Electric current is the flow of electric charge through a conductor. It is measured in amperes (A) and is represented by the symbol "I". The current is directly proportional to the rate of flow of charge, which can be calculated using the formula:

I = Q/t

where:
I = current (A)
Q = charge (coulombs)
t = time (seconds)

Ohm's Law:
Ohm's Law states that the current flowing through a conductor is directly proportional to the voltage across it and inversely proportional to its resistance. Mathematically, it can be expressed as:

V = I * R

where:
V = voltage (V)
I = current (A)
R = resistance (Ω)

Drift of Electrons:
In a conductor, electric current is carried by the movement of electrons. These electrons experience resistance as they move through the conductor due to collisions with atoms and other electrons. This phenomenon is known as the drift of electrons.

Formulae for EMF:
1. In a circuit with a single source of EMF:
The EMF (E) is equal to the potential difference (V) across the terminals of the source when no current is flowing, and can be calculated using the formula:

E = V

2. In a circuit with multiple sources of EMF in series:
The total EMF (E_total) is equal to the algebraic sum of the individual EMFs in the circuit. Mathematically, it can be expressed as:

E_total = E1 + E2 + E3 + ...

where:
E_total = total EMF (V)
E1, E2, E3, ... = individual EMFs (V)

3. In a circuit with multiple sources of EMF in parallel:
The total EMF (E_total) is equal to the EMF of the source with the maximum potential difference. Mathematically, it can be expressed as:

E_total = E_max

where:
E_total = total EMF (V)
E_max = maximum EMF among the sources (V)

These formulae for EMF are important in understanding and analyzing electrical circuits. They provide a quantitative understanding of the driving force behind the flow of electric current and help in determining the behavior of the circuit components.