Q188 / 200 · Manipal (MET) 2014 · Physics
Consider the cylindrical element as shown in the figure. Current flowing the through element is $I$ and resistivity of material of the cylinder is $\rho$. Choose the correct option out the following.


- APower loss in first half is four times the power loss in second half
- Correct answerBVoltage drop in first half is twice of voltage drop in second half
- CCurrent density in both halves are equal
- DElectric field in both halves is equal
Solution
$\begin{aligned} \frac{R_1}{R_2}=\frac{A_1}{A_2}= & \frac{4}{1} \\ & \frac{P_1}{P_2}=\frac{I^2 R_1}{I^2 R_2}=\frac{4}{1} \Rightarrow \frac{V_1}{V_2}=\frac{I R_1}{I R_2}=\frac{4}{1} \\ & \frac{J_1}{J_2}=\frac{1}{4}\end{aligned}$
Hence, the correct answer is option: 'B'.