Question

A student used the set up given here to study the dependence of current (I) on the potential difference (V) across a resistor.
He kept the contact C in four different positions marked as P, Q, R and S in the figure. On calculating the values of the ratio $\frac{V}{I}$ for his four readings, he would find that the value of this ratio :



(1) for contact at point P is $\frac{1}{4}\mathrm{th}$ of that for contact at point S.

(2) for contact at point Q is $\frac{2}{4}\mathrm{th}$ of that for contact at point S.

(3) for contact at point R is $\frac{3}{4}\mathrm{th}$ of that for contact at point S.

(4) is the same for all the four readings

Answer 1

According to Ohm's law, $V=IRo\mathrm{r}\frac{V}{I}\text{= R}$ (Where R is a constant and known as the resistance of the circuit)

As the resistance in the circuit is fixed, hence on changing the applied voltage, current in the circuit will also change and the ratio of voltage and current will remain the same for all the four readings. i.e. equal to the resistance of the circuit.

Hence the correct answer is option 4.