NEET Physics Motion of Charged Particle in Magnetic Field MCQs Set A

a)

b)

c)

d)

Answer:

Question:  An electron having a charge e moves with a velocity v in X-direction. An electric field acts on it in Y-direction? The force on the electron acts in

a) negative direction of Y-axis

b) positive direction of Y-axis

c) negative direction of Z-axis

d) positive direction of Z-axis

Answer: negative direction of Y-axis

Question: A charged particle moves through a magnetic field in a direction perpendicular to it. Then the

a) speed of the particle remains unchanged

b) velocity remains unchanged

c) direction of the particle remains unchanged

d) acceleration remains unchanged

Answer: speed of the particle remains unchanged

Question: An electric charge in uniform motion produces

a) both electric and magnetic fields

b) no such field at all

c) a magnetic field only

d) an electric field only

Answer: both electric and magnetic fields

Question:  A charged particle of mass m and charge q travels on a circular path of radius r that is perpendicular to a magnetic field B. The time taken by the particle to complete one revolution is

a)

b)

c)

d)

Answer:

Question:  In cyclotron the gyro-radius is

a) proportional to momentum

b) proportional to energy

c) inversely proportional to momentum

d) inversely proportional to energy

Answer: proportional to momentum

Question: A charge q is moving with a velocity v parallel to a magnetic field B. Force on the charge due to magnetic field is

a) zero

b) B v/q

c) q B/v

d) q v B

Answer: zero

Question: Cyclotron is used to accelerate

a)

b) electrons

c) neutrons

d) negative ions

Answer:

Question:  A positively charged particle enters in a uniform magnetic field with velocity perpendicular to the magnetic field. Which of the following figures shows the correct motion of charged particle?

a)

b)

c)

d)

Answer:

Question:   A charged particle enters in a magnetic field in a direction perpendicular to the magnetic field. Which of the following graphs show the correct variation of kinetic energy of the particle with time t?

a)

b)

c)

d)

Answer:

More Questions.....................................

Question:  The work done by a magnetic field, on a moving charge is

a)

b)

c)

d)

Answer:

Question:  Lorentz force is

a) the vector sum of electrostatic and magnetic force acting on a moving charged particle

b) the vector sum of gravitational and magnetic force acting on a moving charged particle

c) magnetic force acting on a moving charged particle.

d) electrostatic force acting on a charged particle

Answer: the vector sum of electrostatic and magnetic force acting on a moving charged particle

Question:

a) 11 q

b) 5 q

c) 3 q

d) 2 q

Answer: 11 q

Question: A beam of electrons is moving with constant velocity in a region having simultaneous perpendicular electric and magnetic fields of strength 20 Vm^–1 and 0.5 T respectively at right angles to the direction of motion of the electrons. Then the velocity of electrons must be

a) 40 m/s

b) 20 m/s

c) 8 m/s

d) 10 m/s

Answer:  40 m/s

Question:

a) F = 0, if aD = dA

b) F = 0, if aD = –dA

c) F = 0, i f aA = – dD

d) None of these

Answer:  F = 0, if aD = dA

Question:

a)

b)

c)

d)

Answer:

Question:

a)

b)

c)

d)

Answer:

Question:

a)

b)

c)

d)

Answer:

Question:

a) The free electrons of the rod move towards the pivoted end.

b) The free electrons of the rod move towards the outer end

c) The free electrons of the rod move towards the mid-point of the rod.

d) The free electrons of the rod do not move towards any end of the rod as rotation of rod has no effect on motion of free electrons.

Answer: The free electrons of the rod move towards the pivoted end.

Question:   The figure shows a closed loop bent in the form of a semicircle. One bead having charge +q slides from A to B along the diameter in uniform motion and other bead having the same charge slides along the arc from A to B in uniform circular motion. Both take some time to travel from A to B. When both the beads are at the mid-point of their journey, then the forces exerted by lower bead and upper bead are respectively

a) gravitational and electric

b) electric and gravitational

c) magnetic and electric

d) gravitational and magnetic

Answer: gravitational and electric

Question:  A proton moving with a constant velocity passes through a region of space without any change in its velocity. If E and B represent the electric and magnetic fields respectively, this region of space may not have

a)

b)

c)

d)

Answer:

Question:  A charged particle enters into a magnetic field with a velocity vector making an angle of 30º with respect to the direction\ of magnetic field. The path of the particle is

a) straight line

b) helical

c) circular

d) elliptical

Answer: straight line

Question: If an electron and a proton having same momenta enter perpendicular to a magnetic field, then

a) curved path of electron and proton will be same (ignoring the sense of revolution)

b) they will move undeflected

c) curved path of electron is more curved than that of the proton

d) path of proton is more curved

Answer:  curved path of electron and proton will be same (ignoring the sense of revolution)

Question:  In a region, steady and uniform electric and magnetic fields are present. These two fields are parallel to each other. A charged particle is released from rest in this region. The path of the particle will be a

a) straight line

b) circle

c) helix

d) ellipse

Answer: straight line

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

a) zero

b)

c)

d)

Answer:  zero

Question:

a) 16cm

b) 11 cm

c) 18 cm

d) 12cm

Answer: 16cm

Question:  An electron (mass = 9 × 10^–31 kg, charge = 1.6 × 10^–19 C) moving with a velocity of 10⁶ m/s enters a magnetic field. If it describes a circle of radius 0.1m, then strength of magnetic field must be

a) 5.5 × 10^–5 T

b) 4.5 × 10^–5 T

c) 1.4 × 10^–5 T

d) 2.6 × 10^–5 T

Answer:  5.5 × 10^–5 T

Question:

a)

b)

c)

d)

Answer:

Question:  A proton and a deuterium nucleus having certain kinetic energies enter in a uniform magnetic field with same component of velocity in the direction of magnetic field. Which of the following is correct?

a) Deuterium nucleus has greater pitch of helical motion

b) Both particles have same pitch of helical motion.

c) Which particle has greater pitch depends on the fact that which particle has greater component of velocity perpendicular to magnetic field

d) Proton has greater pitch of helical motion.

Answer: Deuterium nucleus has greater pitch of helical motion

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

a) 2.8 MHz

b) 1.4 MHz

c) 2.1 MHz

d) 0.7 MHz

Answer:  2.8 MHz