A potentiometer wire $\mathrm{PQ}$ of $1\mathrm{m}$ length is connected to a standard cell ${\mathrm{E}}_1$. Another cell ${\mathrm{E}}_2$ of emf $1.02 \mathrm{V}$ is connected with a resistance '$\mathrm{r}$' and switch $\mathrm{S}$ (as shown in figure). With switch $\mathrm{S}$ open, the null position is obtained at a distance of $49 \mathrm{cm}$ from$\mathrm{Q}$. The potential gradient in the potentiometer wire is :

• Correct answer
  A

  $0.02 \mathrm{V}/\mathrm{cm}$
• B

  $0.01 \mathrm{V}/\mathrm{cm}$
• C

  $0.03 \mathrm{V}/\mathrm{cm}$
• D

  $0.04 \mathrm{V}/\mathrm{cm}$

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