Question

Explain with diagram what is meant by the series combination" and "parallel combination" of resistances. In which case the resultant resistance is (i) less, and (ii) more, than either of the individual resistances?"

Answer 1

Explanation:

(i) Series combination

When two or more resistances are connected end to end consecutively, they are said to be connected in series combination. The combined resistance of any number of resistances connected in series in equal to the sum of the individual resistances.

R = R1 + R2 + ......

The resultant resistance is more than either of the individual resistances.

(ii) Parallel combination

When two or more resistances are connected between the same two points, they are said to be connected in parallel combination. The reciprocal of the combined resistance of a number of resistances connected in parallel is equal to the sum of the reciprocals of all the individual resistances.

1/R = 1/R1 + 1/R2 + ........

The resultant resistance is less than either of the individual resistances.

Answer 2

Explanation:

Series Combination:

• When the resistors are connected in series i.e., one end of one resistor is connected to one end of the other resistor, the current flowing through all the resistors is same as it is flowing through one single path.
• So, the resultant resistance is equal to the sum of the individual resistances.

        $\text { i.e., RSeries }=R 1+R 2+R 3+\cdots \ldots$

Parallel Combination:

• When the resistors are connected in parallel, the potential difference across two points is same in each resistor.
• So, the resultant resistance is equal to the sum of the reciprocal of their individual resistances.

        $\text { i.e., RParallel }==\frac{1}{R 1}+\frac{1}{R 2}+\frac{1}{R 3}+\cdots \ldots$

• (i) The resultant resistance is less in case of parallel combination than either of the individual resistances.
• (ii) In series combination, the resultant resistance is more than either of the individual resistances.