8 A parallel plate capacitor of capacity 100𝜇F is charged by a battery of 50 volts. The battery remains connected and if the plates of the capacitor are brought closer so that the distance between them becomes half the original distance, the additional energy given by the battery to the capacitor in joules is: a) 1.25 × 10ିଷ b) 0.125 × 10ିଷ c) 12.5 × 10ିଷ d) 125 × 10ିଷ 9 Two cities are 150 km apart. Electric power is sent from one city to another city through copper wires. The fall of potential per km is 8 volt and the average resistance per km is 0.5𝛺 . The power loss in the wires is: a) 19.2 kW b) 12.2J c) 12.2kW d) 19.2 J 10 The resistivity of the potentiometer wire is 10ି଻ 𝛺 m. Its area of cross - section is 10 ି଺ m ଶ . When a current I = 0.1. A flow through the wire, its potential gradient is: a) 10ିସ Vm ିଵ b) 10Vmିଵ c) 10ିଶ Vm ିଵ d) 0.1 Vm ିଵ 11 A set of n equal resistors, of value R each, are connected in series to a battery of emf 𝜀 and internal resistance R. The current drawn is I. Now, the n resistors are connected in parallel to the same battery. Then the current drawn from battery becomes 10 I. The value of n is: a) 10 b) 11 c) 20 d) 9 12 According to Kirchhoff’s Junction Rule, a) none of these b) At any junction of circuit elements, the sum of currents entering and leaving the junction must be positive.c) At any junction of circuit elements, the sum of currents entering the junction must equal the sum of currents leaving it. d) At any junction of circuit elements, the sum of currents entering and leaving the junction must be negative. 13 A galvanometer having a resistance of 8𝛺 is shunted by a wire of resistance 2 𝛺 . If the total current is 1 A, the part of it passing through the shunt will be: a) 0.8 A b) 0.3 A c) 0.5 A d) 1.2 A 14 A circular coil A has a radius a and the current flowing in it is I. Another circular coil B has a radius 2a and if 2lis the current flowing through it, then the magnetic fields at the centre of the circular coils are in the ratio of: a) 3 : 1 b) 4 : 1 c) 1 : 1 d) 2 : 1 15 A galvanometer of resistance 20𝛺 shows a deflection of 10 divisions when a current of 1 mA is passed through it. If a shunt of 4 𝛺 is connected and there are 50 divisions on the scale, the range of the galvanometer is: a) 40 mA b) 30 mA c) 25 mA d) 35 mA 16 According to Gauss’s law for magnetism, a) ∮ 𝐵ሬ⃗. 𝑑𝑠 ሬሬሬሬ⃗ = 0 b) ∫ 𝐵ሬ⃗. 𝑑𝑠 ሬሬሬሬ⃗ = 0 c) ∮ 𝐵ሬ⃗. 𝑑𝑠 ሬሬሬሬ⃗ = 𝜇଴ d) ∫ 𝐵ሬ⃗. 𝑑𝑠 ሬሬሬሬ⃗ = 𝜇଴ 17 A Rowland ring of mean radius 15 cm has 3500 turns of wire wound on a ferromagnetic core of relative permeability 800. What is the magnetic field B in the core for a magnetising current of 1.2A? a) 3.48 T b) 5.48 T c) 4.08 T d) 4.48 T 18 Magnetic field due to a magnet 2 cm long having a pole strength of 100 Am at a point 10 cm from each pole is a) 8 × 10ିସ𝑇 b) 4 × 10ିହ𝑇 c) 2 × 10ିହ𝑇 d) 2 × 10ିସ𝑇