The coil in a tangent galvanometer is 16 cm in radius. If a current of 20 mA is to produce a deflection of 45°, then the number of turns wound on it, is (Take horizontal component of earth's magnetic field = 0.36 x 10-4 T and µ0 = 4π x 10-7 WbA-1 m-1 )
229
458
689
916
A frog can be levitated in magnetic field produced by a current in a vertical solenoid placed below the frog. This is possible because the body of the frog behaves as
paramagnetic
diamagnetic
ferromagnetic
anti-ferromagnetic
The magnetic susceptibility of a material of a rod is 499. The absolute permeability of vacuum is 4 x 10-7 Hm-1 . The absolute permeability of the material of rod is
A small piece of metal wire is dragged across the gap between the poles of a magnet in 0.4 s. If change in magnetic flux in the wire is 8 x 10-4 Wb, then emf induced in the wire is
8 × 10-3 V
6 × 10-3 V
4 × 10-3 V
2 × 10-3 V
The magnetic flux linked with a coil at any instant t is given by the equation : = 5t3 − 100t + 300. The magnitude of emf induced in the coil after 3 s is
10 V
20 V
35 V
70 V
C.
35 V
Minus sign signifies the Lenz's Law.
In 0.1 s, the current in a coil increases from 1 A to 1.5 A. If inductance of coil is 60 mH, then induced current in external resistance of 3Ω will be
1 A
0.5 A
0.2 A
0.1 A
The impedence of a circuit, when a resistance R and an inductor of inductance L are connected in series in an AC circuit of frequency f, is
In a series LCR circuit, resistance R = 10 Ω and the impedance Z = 10 Ω. The phase difference between the current and the voltage is
0°
30°
45°
60°
A circuit consists of an inductance of 0.5 mH and a capacitor of 20 µF. The frequency of the LC oscillations is approximately
400 Hz
88 Hz
1600 Hz
2400 Hz
Which of the following electromagnetic waves have the smallest wavelength ?
γ-rays
X-rays
UV waves
infrared rays