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MHT CET · Physics · Current Electricity

A potentiometer is used to measure the potential difference between \(\mathrm{A}\) and \(\mathrm{B}\), the null point is obtained at \(0.9 \mathrm{~m}\). Now potential difference between \(\mathrm{A}\) and \(\mathrm{C}\) is measured, the null point is obtained at \(0.3 \mathrm{~m}\). The ratio \(\frac{E_2}{E_1}\) is \(\left(E_1>E_2\right)\)

  1. A \(3: 1\)
  2. B \(2: 3\)
  3. C 1:3
  4. D 3:1
Verified Solution

Answer & Solution

Correct Answer

(B) \(2: 3\)

Step-by-step Solution

Detailed explanation

Position of null point is directly proportional to the potential drop, as the resistance of the wire is directly proportional to the length of the wire.
\(\begin{aligned} & \Rightarrow \frac{V_{A B}}{V_{A C}}=\frac{0.9 \mathrm{~m}}{0.3 \mathrm{~m}}=\frac{E_1}{E_1-E_2} \\ & \Rightarrow \frac{E_1}{E_1-E_2}=3---(1)\end{aligned}\)
Subtract one from each side of equation (1)
\(\begin{aligned} & \Rightarrow \frac{E_1}{E_1-E_2}-1=3-1 \\ & \Rightarrow \frac{E_2}{E_1-E_2}=2---(2)\end{aligned}\)
Take the ratio of equation (2) and (1),
\(\Rightarrow \frac{E_2}{E_1}=\frac{2}{3}\)