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This mock test of Test: Magnetic Lorentz Force for Class 12 helps you for every Class 12 entrance exam.
This contains 10 Multiple Choice Questions for Class 12 Test: Magnetic Lorentz Force (mcq) to study with solutions a complete question bank.
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QUESTION: 1

An electron with a speed of 1.8 x 10^{6} m/s is moving in a circular orbit in a uniform magnetic field of 10^{-4} Wb/m², the radius of the circular path of the electron is

Solution:

QUESTION: 2

A uniform electric field and a uniform magnetic field are produced, pointed in the same direction. An electron is projected with its velocity pointing in the same direction

Solution:

Electric field will apply a force opposite to velocity of the electron hence, speed will decrease.

QUESTION: 3

The force acting on a charge q moving with velocityin a magnetic field is given by

Solution:

The magnetic force on a free moving charge is perpendicular to both the velocity of the charge and the magnetic field with direction given by the right hand rule . The force is given by the charge times the vector product of velocity and magnetic field.

QUESTION: 4

A Charge is fired through a magnetic field. The magnetic force acting on it is maximum when the angle between the direction of motion and magnetic field is

Solution:

The force will have a magnitude F=qvB sin q, thus it will be maximum if sin q is maximum. Thus, angle between velocity and magnetic field should be 90^{o} or the charge particle moves perpendicular to the velocity vector.

QUESTION: 5

The frequency (v) of charged particle, moving at right angles to the magnetic field is independent of

Solution:

Frequency (v) = qB/2πm.

Frequency is independent of radius of trajectory of particle and speed of particle.

QUESTION: 6

Find the magnetic force when a charge 3.5C with flux density of 4 units is having a velocity of 2m/s.

Solution:

The magnetic force is given by F = q(v x B), where q = 3.5C, v = 2m/s and B = 4 units. Thus we get F = 3.5(2 * 4) = 28 units.

QUESTION: 7

A proton enters a magnetic field with a velocity of 1.5 x 10^{5} m/s making an angle of 30° with the field. What is the force experienced by the proton if B = 3.0 T.

Solution:

QUESTION: 8

When a charged particle moves in a magnetic field, its kinetic energy always

Solution:

When a charged particle enters a magnetic field B its kinetic energy remains constant as the force exerted on the particle is:

is perpendicular to so the work done by =0. This does not cause any change in kinetic energy.

QUESTION: 9

A proton carrying 1 MeV kinetic energy is moving in a circular path of radius R in the uniform magnetic field. What should be the energy of an alpha particle to describe a circle of the same radius in the same field.

Solution:

Kinetic energy of a charged particle,

Radius of the circular path of a charged particle uniform magnetic field is given by

Mass of a proton, m_{p} = m

Mass of an α-particle. m_{α} = 4m

Charge of a proton, q_{p} = e

Charge of an α -particle, q_{α} = 2_{e
}

QUESTION: 10

An electron is moving in a circular orbit in a magnetic field 2 x 10^{-3} Wb/m², the time period of electron is

Solution:

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