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

The situation is as shown in the figure.For a balanced Wheatstone's bridgePQ=RS ∴10Ω30Ω=30Ω90Ω  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=5Ω+10Ω+30Ω30Ω+90Ω10Ω+30Ω+30Ω+90Ω =5Ω+40Ω120Ω40Ω+120Ω=5Ω+30Ω=35ΩCurrent drawn from the cell isI=7V35Ω=15A=0.2A