Moving Charges and Magnetism — Physics STD 12 Science — Question

A thin semicircular conducting ring of radius R is falling with its plane vertical in a horizontal magnetic induction B. At the position MNQ, the speed of the ring is V and the potential difference developed across the ring is

(a) Zero

(b) Bv and M is at higher potential

(c) πRBV and Q is at higher potential

(d) 2RBV and Q is at higher potential

The narrowest hysterisis loop is for:

Wires 1 and 2 carrying currents  and  respectively are inclined at an angle  θ to each other. What is the force on a small element dl of wire 2 at a distance of r from wire 1 (as shown in figure) due to the magnetic field of wire1

(a)

(b)

(c)

(d)

A 100 watt bulb working on 200 volt and a 200 watt bulb working on 100 volt have

(a) Resistances in the ratio of 4 : 1

(b) Maximum current ratings in the ratio of 1 : 4

(c) Resistances in the ratio of 2 : 1

(d) Maximum current ratings in the ratio of 1 : 2

A potentiometer consists of a wire of length 4 m and resistance 10Ω. It is connected to a cell of e.m.f. 2 V. The potential difference per unit length of the wire will be

(a) 0.5 V/m

(b)  2 V/m

(c)  5 V/m

(d) 10 V/m

Of the following properties, the photon does not process:

The current through choke coil increases form zero to 6A in 0.3 seconds and an induced e.m.f. of 30 V is produced. The inductance of the coil of choke is

(a) 5 H

(b) 2.5 H

(c) 1.5 H

(d) 2 H

A 6kHz sinusoidal voltage is applied to a series RC circuit. The frequency of the voltage across the resistor is.

The average life T  and the decay constant λ of a radioactive nucleus are related as

(a) T λ = 1

(b) T =

(c)

(d) T =