## Class 12 Physics MCQs Moving Charges And Magnetism for JEE/NEET

Here, you will get Class 12 Physics MCQ of Chapter 4 Moving Charges And Magnetism for cracking JEE and NEET/AIIMS. By solving these MCQs of Class 12 Physics Chapter 4 Moving Charges And Magnetism, you will get the confidence to crack JEE or NEET. Practice MCQ Questions for Class 12 Physics with Answers on a daily basis and score well in exams.

## Moving Charges And Magnetism Class 12 MCQs Questions with Answers

Which of the following is not correct about cyclotron?
(a) It is a machine to accelerate charged particles or ions to high energies
(b) Cyclotron uses both electric and magnetic fields in combination to increase the energy of charged particles
(c) The operation of the cyclotron is based on the fact that the time for one revolution of an ion is independent of its speed or radius of its orbit
(d) The charged particles and ions in cyclotron can move on any arbitrary path

Answer: (d) The charged particles and ions in cyclotron can move on any arbitrary path

A short bar magnet has a magnetic moment of 0. 65 J T-1, then the magnitude and direction of the magnetic field produced by the magnet at a distance 8 cm from the centre of magnet on the axis is
(a) 2.5 × 10-4 T, along NS direction
(b) 2.5 × 10-4 T along SN direction
(c) 4.5 × 10-4 T, along NS direction
(d) 4.5 × 10-4 T, along SN direction

Answer: (b) 2.5 × 10-4 T along SN direction

A moving coil galvanometer can be converted into an ammeter by
(a) introducing a shunt resistance of large value in series
(b) introducing a shunt resistance of small value in parallel
(c) introducing a resistance of small value in series
(d) introducing a resistance of large value in parallel

Answer: (b) introducing a shunt resistance of small value in parallel

When a magnetic compass needle is carried nearby to a straight wire carrying current, then
(I) the straight wire cause a noticeable deflection in the compass needle
(II) the alignment of the needle is tangential to an imaginary circle with straight wire as its centre and has a plane perpendicular to the wire

(a) (I) is correct
(b) (II) is correct
(c) both (I) and (II) are correct
(d) neither (I) nor (II) is correct

Answer: (c) both (I) and (II) are correct

A charged particle is moving on circular path with velocity v in a uniform magnetic field B, if the velocity of the charged particle is doubled and strength of magnetic field is halved, then radius becomes
(a) 8 times
(b) 4 times
(c) 2 times
(d) 16 times

A current carrying coil is placed in a uniform magnetic field. If the coil turns through an angle θ, then the torque is directly proportional to
(a) sin θ
(b) cos θ
(c) cot θ
(d) tan θ

What is the angle of dip at the magnetic poles?
(a) 30°
(b) 0°
(c) 45°
(d) None of these

Circular loop of radius 0.0157 m carries a current 2 A. The magnetic field at the centre of the loop is
(a) 1.57 × 10-3Wb/m²
(b) 8.0 × 10-5 Wb/m²
(c) 2.0 × 10-3 Wb/m²
(d) 3.l4 × 10-1 Wb/m²

Answer: (b) 8.0 × 10-5 Wb/m²

When we double the radius of a coil keeping the current through it unchanged, what happens to the magnetic field directed along its axis at far off points?
(a) halved
(b) doubled
(d) remains unchanged

A current carrying power line carries current from west to east. Then the direction of the magnetic field 2 m above it is
(a) west to east
(b) south to north
(c) north to south
(d) None of these

According to Gauss’s theorem in magnetism, surface integral of magnetic field intensity over a surface (closed or open) is always
(a) -1
(b) 1
(c) 0
(d) infinity

The magnetic moment of a current I carrying circular coil of radius r and number of turns N varies as
(a) 1r²
(b) 1r
(c) r
(d) r²

A charged particle of mass m and charge q travels on a circular path of radius r i.e., perpendicular to the magnetic field B. The time taken by particle to complete on revolution is
(a) 2πqB/m
(b) 2πm/qB
(c) 2πmq/B
(d) 2πq2B/m

A cubical region of space is filled with some uniform electric and magnetic fields. An electron enters the cube across one of its faces with velocity v and a positron enters via opposite face with velocity -v. At this instant,
(a) the electric forces on both the particles cause identical accelerations
(b) the magnetic forces on both the particles cause equal accelerations
(c) Only electron gains or looses energy
(d) the motion of the centre of mass (CM) is determined by E alone

Answer: (b) the magnetic forces on both the particles cause equal accelerations

The magnetic field produced by an / meter long straight (x cry thin) current (I) carry ing conductor at any point on itself is
(a) zero
(b) infinite
(c) µ0l/4πl
(d) µ0l/2πl

The magnetic field of a given length of a ware for single turn coil at its centre is B. Then.its value for two turns of coil will be
(a) B/4
(b) B/2
(c) 4B
(d) 2B

Isoclinic lines are the lines joining places with
(a) equal dip
(b) equal declination
(cj equal dip and declination
(d) None of these

Two a-particles have the ratio of their velocities as 3 : 2 on entering the field. If they move in different circular paths, then the ratio of the radii of their paths is
(a) 2 : 3
(b) 3 : 2
(c) 9 : 4
(d) 4 : 9

Which of the following is not a unit of magnetic induction?
(a) gauss
(b) tesla
(c) oersted
(d) weber/metre²

A charge + q is sent through a magnetic field. The force acting on it is maximum w hen the angle between the direction of motion of the charged particle and the magnetic field
(a) 0°
(b) 45°
(c) 90°
(d) 180°

10 eV electron is circulating in a plane at right angle to a uniform field of magnetic induction 10-1 Wb/m² (1G). The orbital radius of electron is
(a) 12 cm
(b) 16 cm
(c) 11 cm
(d) 18 cm

A cyclotron can be used to produce high energy
(a) neutrons
(b) deutrons
(c) β particles
(d) α particles

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

Answer: (a) undergoes acceleration all the time

The most suitable metal for making permanent magnets is
(a) iron
(b) steel
(c) copper
(d) aluminium