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

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: A

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: A

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: A

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: A

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: A

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: A

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: A

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: A

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: A

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: A

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: A

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: A

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: A