Direction: A potentiometer is device used for measuring emf and internal resistance of a cell. It consists of two circuits one is main circuit in which there is a cell of given emf\[\varepsilon \] and given resistance R which is connected across a wire of length 100 cm having resistance r. Another circuit having unknown emf\[\varepsilon \]and galvanometer. For a given potentiometer if \[\varepsilon '=30\,V,\,\,r=1\Omega \] and resistance R varies with time t given by\[R=2t\]. The jockey can move on wire with constant velocity 10 cm/s and switch S is closed at\[t=0\]. |
A) 1 s
B) 2 s
C) 3 s
D) 4 s
Correct Answer: C
Solution :
As, \[\varepsilon =\frac{30\times 0.7}{2(t+7)+1}=1\]\[\Rightarrow \]\[t=3\,\,s\]You need to login to perform this action.
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