NEET Physics Moving Charges and Magnetism MCQs Set A

a) The charge to mass ratio satisfy

b) They necessarily represent a particle, anti-particle pair

c) They must have equal charges

d) They have equal z-components of momenta

Answer: The charge to mass ratio satisfy

Question: Biot-Savart law indicates that the moving electrons (velocity v) produce a magnetic field B such that

a) B is perpendicular of

b) B is parallel to v

c) it obeys inverse cube law

d) it is along the line joining the electron and point of observationt

Answer: B is perpendicular of

Question: A current carrying circular loop of radius R is placed in the x-y plane with centre at the origin. Half of the loop with x > 0 is now bent so that it now lies in the y-z plane

a) The magnitude of magnetic moment now diminishes

b) The magnetic moment does not change

c) The magnitude of B at (0, 0, z), z > R increases

d) The magnitude of B at (0, 0, z), z >> R is unchanged

Answer: The magnitude of magnetic moment now diminishes

Question: An electron is projected with uniform velocity along the axis of a current carrying long solenoid. Which of the following is true?

a) The electron will continue to move with uniform velocity along the axis of the solenoid

b) The electron will experience a force at 45° to the axis and hence execute a helical path

c) The electron path will be circular about the axis

d) The electron will be accelerated along the axis

Answer: The electron will continue to move with uniform velocity along the axis of the solenoid

Question: In a cyclotron, a charged particle

a) undergoes acceleration all the time

b) speeds up between the dees because of the magnetic field

c) speeds up in a dees

d) slows down within a dee and speeds up between dees

Answer: undergoes acceleration all the time

Question:   Two identical long conducting wires AOB and COD are placed at right angle to each other, with one above other such that ‘O’ is their common point for the two. The wires carry I1 and I2 currents respectively. Point ‘P’ is lying at distance ‘d’ from ‘O’ along a direction perpendicular to the plane containing the wires. The magnetic field at the point ‘P’ will be :

a)

b)

c)

d)

Answer:

Question:  If we double the radius of a coil keeping the current through it unchanged, then the magnetic field at any point at a large distance from the centre becomes approximately

a) four times

b) double

c) three times

d) one-fourth

Answer:  four times

Question:

a) 2.97 W

b) 1.57 W

c) 14.85 W

d) 29.7 W

Answer:  2.97 W

Question:

a)

b)

c)

d) None of these

Answer:

Question:   A proton and an alpha particle both enter a region of uniform magnetic field B, moving at right angles to field B. If the radius of circular orbits for both the particles is equal and the kinetic energy acquired by proton is 1 MeV the energy acquired by the alpha particle will be:

a) 1 MeV

b) 0.5 MeV

c) 1.5 MeV

d) 4 MeV

Answer: 1 MeV

Question:  A portion of a conductive wire is bent in the form of a semicircle of radius r as shown below in fig. At the centre of semicircle, the magnetic induction will  be

a)

b)

c) infinite

d) zero

Answer:

Question:  A rectangular loop of sides 10 cm and 5 cm carrying a current 1 of 12 A is placed in different orientations as shown in the figures below :

a) (B) and (D), respectively

b) (B) and (C), respectively

c) (A) and (B), respectively

d) (A) and (C), respectively

Answer: (B) and (D), respectively

Question: A charged particle moving in a uniform magnetic field and losses 4% of its kinetic energy. The radius of curvature of its path changes by

a) 2%

b) 4%

c) 10%

d) 12%

Answer: 2%

Question:  Two particles X and Y having equal charges, after being accelerated through the same potential difference, enter a region of uniform magnetic field and describe circular paths of radii R₁ and R₂, respectively. The ratio of masses of X and Y is

a)

b)

c)

d)

Answer:

Question:

a)

b)

c)

d)

Answer:

Question:

a) 1/4

b) 1/2

c) 1

d) 4

Answer: 1/4

Question:  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

a)

b)

c)

d)

Answer:

Question: Assertion : Free electrons always keep on moving in a conductor even then no magnetic force act on them in magnetic field unless a current is passed through it.
Reason : The average velocity of free electron is zero.

a) Assertion is correct, reason is correct; reason is not a correct explanation for assertion

b) Assertion is correct, reason is incorrect

c) Assertion is incorrect, reason is correct.

d) Assertion is correct, reason is correct; reason is a correct explanation for assertion

Answer: Assertion is correct, reason is correct; reason is not a correct explanation for assertion

Question:

a)

b)

c)

d)

Answer:

Question:  A deuteron of kinetic energy 50 keV is describing a circular orbit of radius 0.5 metre in a plane perpendicular to the magnetic field B. The kinetic energy of the proton that describes a circular orbit of radius 0.5 metre in the same plane with the same B is

a) 100 keV

b) 50 keV

c) 25 keV

d) 200 keV

Answer:  100 keV

Question:

v

a)

b)

c)

d)

Answer:

Question:   An arrangement of three parallel straight wires placed perpendicular to plane of paper carrying same current 'I along the same direction is shown in fig. Magnitude of force per unit length on the middle wire 'B' is given by

a)

b)

c)

d)

Answer:

Question:  A coil of circular cross-section having 1000 turns and 4 cm² face area is placed with its axis parallel to a magnetic field which decreases by 10^–2 Wb m^–2 in 0.01 s. The e.m.f. induced in the coil is:

a) 400 mV

b) 4 mV

c) 200 mV

d) 0.4 mV

Answer: 400 mV

Question:  A charged particle moves through a magnetic field perpendicular to its direction. Then

a) the momentum changes but the kinetic energy is constant

b) both momentum and kinetic energy of the particle are not constant

c) both momentum and kinetic energy of the particle are constant

d) kinetic energy changes but the momentum is constant

Answer: the momentum changes but the kinetic energy is constant

Question:  Two very long, straight, parallel wires carry steady currents I and -I respectively. The distance between the wires is d. At a certain instant of time, a point charge q is at a point equidistant from the two wires, in the plane of the wires. Its instantaneous velocity v is perpendicular to this plane. The magnitude of the force due to the magnetic field acting on the charge at this instant is

a) 

b)

c)

d)

Answer:

Question:   Current sensitivity of a moving coil galvanometer is 5 div/ mA and its voltage sensitivity (angular deflection per unit voltage applied) is 20 div/V. The resistance of the galvanometer is

a)

b)

c)

d)

Answer:

Question:  A metallic rod of mass per unit length 0.5 kg m^–1 is lying horizontally on a smooth inclined plane which makes an angle of 30° with the horizontal. The rod is not allowed to slide down by flowing a current through it when a magnetic field of induction 0.25 T is acting on it in the vertical direction. The current flowing in the rod to keep it stationary is

a) 11.32 A

b) 14.76 A

c) 5.98 A

d) 7.14 A

Answer: 11.32 A

Question: Assertion: The frequency of circular motion of a charged particle in cyclotron is independent of the mass of the particle.
Reason: Greater the mass of the particle less will be the frequency of the particle.

a) Assertion is incorrect, reason is correct

b) Assertion is correct, reason is incorrect

c) Assertion is correct, reason is correct; reason is not a correct explanation for assertion

d) Assertion is correct, reason is correct; reason is a correct explanation for assertion.

Answer:  Assertion is incorrect, reason is correct

Question:

a)

b)

c)

d)

Answer:

Question: A charged particle enters in a uniform magnetic field with a certain velocity. The power delivered to the particle by the magnetic field depends on

a) None of these

b) angular speed w and acceleration of the particle

c)

d)

Answer:  None of these

Question:

a)

b)

c)

d)

Answer:

Question:  You are given a closed circuit with radii a and b as shown in fig carrying current i. The magnetic dipole moment of thecircuit is

a)

b)

c)

d)

Answer:

Question:  A wire of length L metre carrying a current I ampere is bent in the form of a circle. Its magnitude of magnetic moment will be

a)

b)

c)

d)

Answer:

Question:

a) 1.05 × 10^–2 weber/m²

b) 1.05 × 10^–3 weber/m²

c) Both

d) None of these

Answer: 1.05 × 10^–2 weber/m²

Question:  A steady current I flows down a hollow cylindrical tube of radius a and is uniformly distributed around the tube. Let r be the distance from the axis of symmetry of the tube to a given point. What is the magnitiude of the magnetic field B at a point inside the tube?

a) 0

b) 2 I/r c

c) 2 I r/a²c

d) None of these

Answer:  0

Question:

a)

b)

c)

d)

Answer:

Question:  Of n sides which can be inscribed in a circle of radius R. The magnetic field induction at the center of polygon due to one side of the polygon is

a)

b)

c)

d) None of these

Answer:

Question:  A coil having N turns is wound tightly in the form of a spiral with inner and outer radii a and b respectively. When a current I passes through the coil, the magnetic field at the center is

a)

b)

c)

d)

Answer:

Question:   Consider a hypothetic spherical body. The body is cut into two parts about the diameter. One of hemispherical portion has mass distribution m whie the other portion has identical charge distribution q. The body is rotated about the axis with constant speed w. Then, the ratio of magnetic moment to angular momentum is

a)

b)

c)

d)  cannot be calculated

Answer:

Question:

a)

b)

c)

d)

Answer:

Question:

a) 7

b) 4

c) 5

d) 6

Answer: 7

Question:  The length of a solenoid is 0.4 m and the number turns in it is 500. A current of 3 amp, is flowing in it. In a small coil of radius 0.01 m and number of turns 10, a current of 0.4 amp. is flowing. The torque necessary to keep the axis of this coil perpendicular to the axis of solenoid will be

a) 5.92 × 10^–6 N-m

b) 5.92 × 10^–4 N-m

c) 5.92 × 10^–4 dyne-cm

d) 5.92 × 10^–6 dyne-cm

Answer:  5.92 × 10^–6 N-m

Question:

a)

b)

c)

d)

Answer:

Question:

a) Zero

b) 2.0 × 10^–7 T

c) 2.0 × 10^–7 T

d) 1.63 × 10^–11 T

Answer:  Zero

Question:

a)

b)

c)

d)

Answer: