Resistors are sometimes joined together. There are two types
of Combinations of resistors and these are:
- Series Combination
- Parallel Combination
Equivalent resistance of the combination is defined as a single resistance which allows the same current to flow as the given
combination when the same potential difference is applied across it.
Series Combination
Two resistors are said to be in series if only one of their
end points is joined. Same current
passes through all the resistors of a Series Combination.
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| Series Combination of Resistors |
From the above circuit,
V = V1 + V2
Or, IR= IR1 + IR2
Or, R = R1 + R2
Thus the equivalent resistance of
a series combination of resistors is equal to the sum of individual
resistances.
Parallel Combination
Two or more resistors are said to
be in parallel if one end of all the resistors is joined together and similarly
the other ends joined together. In parallel combination, same potential
difference exists across all resistors.
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| Parallel Combination of Resistors |
From the above circuit,
I = I1 + I2
Or, V/R = V(1/R1 + 1/R2)
Or, 1/R = 1/R1 + 1/R2
Thus reciprocal of equivalent resistance of
parallel combination is equal to the sum of the reciprocals of individual
resistances.
