Question -
In the electrical circuit shown in figure the current through the galvanometer will be zero if the value of resistance x is
Options:
A .  4 ohm
B .  8 ohm
C .  16 ohm
D .  24 ohm
Answer: Option D : D The given circuit is Wheatstone's bridge.The current through the galvanometer will be zero if the bridge is balanced PQ+RS where P = 2+3 =5ohm, Q = 10ohm and R=4ohm The value of S is given by 510=4S or S= 8 ohm thus the effective resistance of the parallel combination of 12 ohm and x ohm must be 8 ohm therefore 112+1x=18 which gives x = 24ohm
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