A long wire carrying a steady current is bent into a circular loop of one turn. The magnetic field at the center of loop is B. It is then bent into a circular coil of n turns. The magnetic field at the centre of this coil of n turns will be
1. nB
2.
3. 2nB
4.
An electron is moving in a circular path under the influence of a transverse magnetic field of T. If the value of e/m is C/kg, the frequency of revolution of the electron is
1. 1 GHz
2. 100 MHz
3. 62.8 MHz
4. 6.28 MHz
A square loop ABCD carrying a current i, is placed near and coplanar with a long straight conductor XY carrying a current I, the net force on the loop will be:
1.
2.
3.
4.
A wire carrying current l has the shape as shown in the adjoining figure. Linear parts of the wire are very long and parallel to X-axis while the semicircular portion of radius R is lying in the Y-Z plane. Magnetic field at point O is :
1.
2.
3.
4.
An electron moving in a circular orbit of radius r makes n rotations per second. The magnetic field produced at the centre has magnitude:
A circuit contains an ammeter, a battery of 30 V and a resistance 40.8Ω all connected in series. If the ammeter has a coil of resistance 480Ω and a shunt of 20Ω then reading in the ammeter will be :
(1) 0.5A
(2) 0.25A
(3) 2A
(4) 1A
In an ammeter 0.2% of main current passes through the galvanometer. If resistance of galvanometer is G, the resistance of ammeter will be
(1)
(2)
(3)
(4)
Two similar coils of radius R are lying concentrically with their planes at right angles to each other. The currents flowing in them are I and 2I, respectively. The resultant magnetic field induction at the centre will be
(1)
(2)
(3)
(4)
A millivoltmeter of 25 mV range is to be converted into an ammeter of 25 A range. The value (in ohm) of necessary shunt will be:
(1)0.001
(2)0.01
(3)1
(4)0.05
An alternating electric field of frequency v, is applied across the dees (radius=R) of a cyclotron that is being used to accelerate protons(mass=m).The operating magnetic field (B) used in the cyclotron and the kinetic energy (K) of the proton beam, produced by it, are given by
(1)B=
(2)B=
(3)B=
(4)B=