What is the difference between emf and
potential difference?
As per the definition the emf or the
electromotive force describes the force required to separate two charges at a
given distance. Originally, emf was supposed to relate to problems involving
moving charges, but early on, emf got adopted as being synonymous with
"battery" or "voltage source".
Potential difference is simply a voltage difference between two points
in a closed electrical circuit with a voltage source circuit (or in free
space). So, the interesting fact is the potential difference can be a source of
emf if it is used to move charges. The term ‘potential difference’ is a general
term and found in all the energy fields such as electric, magnetic and
gravitational fields. But emf is only pertaining to electrical circuits.
Although, both ‘electrical potential difference’ and emf are measured in Volts
(V), there are many differences between them.
Potential
Difference
Potential is a function of the location, and potential difference
between point A and point B is calculated by subtracting the potential of A
from potential of B. In an electric field, it is the amount work to be done to
move a unit charge (+1 Coulomb) from B to A. Electric potential difference is
measured in V (Volts). In an electrical circuit, current flows from the higher
potential to lower potential.
EMF
(Electromotive Force)
EMF is the electrical potential difference provided by an energy source
like battery. Varying magnetic fields also can generate an EMF according to the
Faraday’s law. Although EMF is also a voltage and measured in Volts (V), it is
all about the generation of a potential difference.
So the important differences between Voltage and EMF is:
- The
term ‘potential difference’ is used in all energy fields (electric,
magnetic, gravitational), and ‘EMF’ is only used in electric circuits.
- EMF
is the electrical potential difference generated by a source like battery
or generator.
- We
can measure potential difference between any two points, but EMF exists
only between the two ends of a source.
- Sum
of ‘potential drops’ around a circuit is equal to total EMF according to
Kirchhoff’s second law.
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