Q144 / 155 · WBJEE 2016 · Physics

Two equal resistances, $400 \Omega$ each, are connected in series with a $8 \mathrm{V}$ battery. If the resistance of first one increases by $0.5 \%$, the change required in the resistance of the second one in order to keep the potential difference across it unaltered is to

  • A
    increase it by $1 \Omega$
  • Correct answer
    B
    increase it by $2 \Omega$
  • C
    increase it by $4 \Omega$
  • D
    decrease it by $4 \Omega$

Solution

In series combination, $$ R=R_{1}+R_{2} $$ Same current will pass in $A_{1}$ and $R_{2}$. According to question, $R_{1}$ is increased by $0.5 \%$ $\therefore$ Increment in the resistance $$ \begin{array}{l} =\frac{0.5}{100} \times 400 \\ =2.0 \Omega \end{array} $$ So to keep the potential unchanged in second resistance the change required will be $2.0 ~ \Omega$ increment.

Hence, the correct answer is option: 'B'.

Relevant Questions