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
B.
diamagnetic
When diamagnetic substances are placed in a magnetic field, then they are feebly repelled in the field. Frog is leviated in magnetic field produced by the current in vertical solenoid below the frog due to repulsion, so body of frog behaves as diamagnetic substance.
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
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