A cell is connected between two points of a uniformly thick circular conductor and i and i₂ are the currents flowing in two parts of the circular conductor of radius a. The magnetic field at the centre of the loop will be

zero
\(\frac{\mu _{0}}{4\pi}(I_{1}-I_{2})\)
\(\frac{\mu _{0}}{2a}(I_{1}+I_{2})\)
\(\frac{\mu _{0}}{a}(I_{1}-I_{2})\)

Solution

A proton and an α-particle enter a uniform magnetic field perpendicularly with the same speed. If proton takes 25 μ second to make 5 revolutions, then the time period for the α-particle would be

50 μ sec
25 μ sec
10 μ sec
5 μ sec

Solution

A deutron of kinetic energy 50 keV is describing a circularorbit of radius 0.5m, in a plane perpendicular to magnetic field \(\underset{B}{\rightarrow}\). The kinetic energy of a proton that discribes a circular orbit of radius 0.5 m in the same plane with the same magnetic field \(\underset{B}{\rightarrow}\)is

200 keV
50 keV
100 keV
25 keV

Solution

The orbital speed of electron orbiting around a nucleus in a circular orbit of radius 50 pm is 2.2 × 10⁶ ms^–1. Then the magnetic dipole moment of an electron is

1.6 × 10^–19 Am²
5.3 × 10^–21 Am²
8.8 × 10^–24Am²
8.8 × 10^–26 Am²

Solution

If an electron describes half are volution in a circle of radius r in a magnetic field B, the energy acquired by it is

zero
¹⁄₂mv²
¹⁄₄mv²
πr × Bev

Solution

Since magnetic force is always perpendicular to the velocity of electron, so it can only change the direction of velocity of electron, but it (the magnetic force) cannot accelerate or deaccelerate the electron.

A horizontal overhead powerline is at height of 4m from the ground and carries a current of 100 A from east to west.The magnetic field directly below it on the ground is (μ₀ = 4π × 10^–7 Tm A^–1)

2.5 × 10^–7 T southward
5 × 10^–6 T northward
5 × 10^–6 T southward
2.5 × 10^–7 T northward

Solution

Two thin, long, parallel wires, separated by a distance ‘d’carry a current of‘i’ A in the same direction.They will

repel each other with a force of μ₀i²/(2πd)
attract each other with a force of μ₀i²/(2πd)
repel each other with a force of μ₀i²/(2πd²)
attract each other with a force of μ₀i²/(2πd²)

Solution

A circular loop of area 0.02 m² carrying a current of 10A, is held with its plane perpendicular to a magnetic field induction 0.2 T. The torque acting on the loop is

0.01 Nm
0.001 Nm
zero
0.8 Nm

What is cyclotron frequency of an electron with an energy of 100 e V in the earth’s magnetic field of 1 × 10–4 weber / m² if its velocity is perpendicular to magnetic field?

0.7 MHz
2.8 MHz
1.4 MHz
2.1 MHz

Under the influence of a uniform magnetic field a charged particle is moving in a circle of radius R with constant speed v.The time period of the motion

depends on both R and v
is independent of both R and v
depends on R and not v
depends on v and not on R

Solution

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