The resistances of the four arms P, Q, Rand Sin a Wheatstone's bridge are $$10$$ ohm, $$30$$ ohm, $$30$$ ohm and $$90$$ ohm, respectively. The e.m.f. and internal resistance of the cell are $$7$$ volt and $$5$$ ohm respectively. $$1f$$ the galvanometer resistance is $$50$$ ohm, the current drawn from the cell will be

Question

The resistances of the four arms P, Q, Rand Sin a Wheatstone's bridge are $$10$$ ohm, $$30$$ ohm, $$30$$ ohm and $$90$$ ohm, respectively. The e.m.f. and internal resistance of the cell are $$7$$ volt and $$5$$ ohm respectively. $$1f$$ the galvanometer resistance is $$50$$ ohm, the current drawn from the cell will be

Infinity Learn · Accepted Answer

The situation is as shown in the figure.For a balanced Wheatstone's $$bridgePQ=RS$$ ∴$$10$$Ω$$30$$Ω$$=30$$Ω$$90$$Ω  or  $$13=13It$$ is a balanced Wheatstone's bridge. Hence no current flows in the galvanometer arm. Hence, resistance $$50$$ Q becomes ineffective.∴The equivalent resistance of the circuit $$isReq=5$$Ω$$+10$$Ω$$+30$$Ω$$30$$Ω$$+90$$Ω$$10$$Ω$$+30$$Ω$$+30$$Ω$$+90$$Ω $$=5$$Ω$$+40$$Ω$$120$$Ω$$40$$Ω$$+120$$Ω$$=5$$Ω$$+30$$Ω$$=35$$ΩCurrent drawn from the cell $$isI=7V35$$Ω$$=15A=0.2A$$

The resistances of the four arms P, Q, Rand Sin a Wheatstone's bridge are 10 ohm, 30 ohm, 30 ohm and 90 ohm, respectively. The e.m.f. and internal resistance of the cell are 7 volt and 5 ohm respectively. 1f the galvanometer resistance is 50 ohm, the current drawn from the cell will be

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