Torque on current loop, moving coil galvanometer, conversion to ammeter and voltmeter
- Current sensitivity of a moving coil galvanometer is 5 div/mA and its voltage sensitivity (angular deflection per unit voltage applied) is 20 div/V. The resistance of the galvanometer is Answer: 2. 250 Ω Current sensitivity I_s=θ/I and voltage sensitivity V_s=θ/V . Since V=IG , V_s=I_s/G . G=I_s/V_s=5\ div/mA/20\ div/V=frac5\... 1
- A 250 - Turn rectangular coil of length 2.1 cm and width 1.25 cm carries a current of 85 μA and subjected to a magnetic field of strength 0.85 T. Work done for rotating the coil by 180^° against the torque is : Answer: 4. 9.1 μ J Key idea: work done in rotating a coil from θ=0 to 180^° is W=MB(cos0-cos180)=2MB , with M=NIA . A=2.1×10⁻²×1.25×10⁻²=2.6... 1