In the circuit, the galvanometer G shows zero deflection. If the batteries A and B have negligible internal resistance, the value of the resistor R will be [AIEEE 2005] |
A) \[200\,\Omega \]
B) \[100\,\Omega \]
C) \[500\,\Omega \]
D) \[1000\,\Omega \]
Correct Answer: B
Solution :
[b] The galvanometer shows zero deflection i.e., current throughis zero. |
As a result potential drop acrossis 2V, circuit can be redrawn as |
\[l=\frac{12}{500+R}\] |
Voltage across R, |
\[V=lR\] |
\[\Rightarrow \,\,2=\frac{12}{500+R}\times R\] |
\[\Rightarrow \,\,1000\,+2R=12R\,\Rightarrow R=100\Omega \] |
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