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Worksheet on Moving charges and magnetism

Q1 A stationary magnet does not interact with :-


a) iron rod

b) moving charge

c) moving magnet d) stationary charge



Q2 Two infinite long parallel wires carrry equal currents in same direction. The magnetic field at a mid point in between the two wire is :-


a) Twice the magnetic field produced due to each of the wires

b) Half of the magnetic field produced due to each of the wires

c) Square of the magnetic field produced due to each of the wires d) Zero



Q3 Which of the following statement is not true; magnetic field at the centre of current carrying loop :-


a) proportional to current

b) inversely proportional to radius

c) proportional to number of turns d) none



Q4 If radius of coil becomes two times and current becomes half then magnetic field at centre of the coil will be :-


a) Two times

b) Four times

c) Half d) One fourth



Q5 In a current carrying long solenoid the field produced does not depend on :-


a) number of turns per unit length

b) current is solenoid

c) radius of cross section of the solenoid d) all of the above



Q6 If length and number of turns becomes half for a solenoid then value of magnetic field becomes :-


a) twice

b) same

c) half d) one fourth



Q7 If an electron enters a magnetic field with its velocity pointing in the same direction as the magnetic field then :-


a) the electron will turn towards right

b) the electron will turn towards left

c) the velocity of the electron will increase d) the velocity of the electron will remain unchanged



Q8 When a charged particle enters in a uniform magnetic field its kinetic energy :-


a) remains constant

b) increases

c) decreases d) becomes zero



Q9 A charged particle moves through a magnetic field in a direction perpendicular to it. Then the :-


a) speed of the particle remains unchanged

b) direction of motion of particle remains unchanged

c) acceleration of particle remains unchanged d) velocity of particle remains unchanged



Q10 A magnetic field :-


a) Always exerts a force on charged particle

b) Never exerts a force on charged particle

c) Exert a force, if the charged particle is moving across the magnetic field line d) Exerts a force, if the charged particle is moving along the magnetic field line



Q11 Magnetic field lines produced by a bar magnet, cuts each other :-


a) At neutral points

b) Near the poles of the magnets

c) At equatorial axis d) Never intersects to each other



Q12 A beam of electrons passes undeflected through mutually perpendicular electric and magnetic fields. If the electric field is switched off, and the same magnetic field is maintained, the electrons move :-


a) along a straight line

b) in an elliptical orbit

c) in a circular orbit d) along a parabolic path



Q13 A current loop in a magnetic field :-


a) Can be in equilibrium in two orientations, one stable while the other is unstable.

b) Experiences a torque whether the field is uniform or non uniform in all orientations

c) Can be in equilibrium in one orientation d) Can be in equilibrium in two orientations, both the equilibrium states are unstable



Q14 A circular coil placed in a uniform magnetic field. If alternating current flows through this coil then :-


a) net force will act on coil

b) coil will be stationary

c) coil will be rotated d) none of the above



Q15 Assertion :- If a charged particle is moving in perpendicular uniform magnetic field, its kinetic energy does not change

Reason :- Velocity of charge particle is not changing in magnetic field


a) A

b) B

c) C d) D



Q16 Assertion :- A current element is a source of magnetic field.

Reason :- A moving charge is a source of magnetic field.


a) A

b) B

c) C d) D



Q17 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 be accelerated along the axis.

b) The electron path will be circular about the axis.

c) The electron will experience a force at 45 degree to the axis and hence execute a helical path. d) The electron will continue to move with uniform velocity along the axis of the solenoid.



Q18 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.



Q19 A circular coil of radius 4 cm and of 20 turns carries a current of 3 amperes. It is placed in a magnetic field of intensity of 0.5 weber/m to the power (2). the magnetic dipole moment of the coil is.


a) 0.15 ampere–m to the power (2)

b) 0.3 ampere– m to the power (2)

c) 0.45 ampere–m to the power (2) d) 0.6 ampere–m to the power (2)



Q20 If a charged particle moves through a magnetic field perpendicular to it.


a) both momentum and energy of particle change.

b) momentum as well as energy are constant.

c) energy is constant but momentum changes. d) momentum is constant but energy changes.



Q21 A current carrying closed loop of an irregular shape lying in more than one plane when placed in uniform magnetic field, the force acting on it.


a) will be more in the plane where its larger position is covered.

b) is zero.

c) is infinite. d) may or may not be zero.



Q22 The maximum current that can be measured by a galvanometer of resistance 40 Ω is 10 mA. It is converted into voltmeter that can read upto 50 V. The resistance to be connected in the series with the galvanometer is.


a) 2010 Ω

b) 4050 Ω

c) 5040 Ω d) 4960 Ω



Q23 A current loop placed in a non-uniform magnetic field experiences.


a) a force of repulsion.

b) a force of attraction.

c) a torque but not force. d) a force and a torque.



Q24 For the magnetic field to be maximum due to a small element of current carrying conductor at a point, the angle between the element and the line joining the element to the given point must be.


a) 0 degree

b) 90 degree

c) 180 degree d) 45 degree



Q25 A wire is turned into circles with 100 turns of radius 35 cm. What current should be passed through it to produce a magnetic field of 1 T at its centre?


a) 557 A

b) 55 A

c) 5573 A d) None



Q26 A coil of one loop is made by a wire of length L and there after a coil of two loops is made by same wire. The ratio of magnetic field at the centre of coils respectively :-


a) 1 : 4

b) 1 : 1

c) 1 : 8 d) 4 : 1



Q27 A current carrying wire is arranged at any angle in an uniform magnetic field, then


a) only force acts on wire

b) only torque acts on wire

c) both d) none



Q28 A charge particle is moving in the direction of a magnetic field. The magnetic force acting on the particle :-


a) is in the direction of its velocity

b) is in the direction opposite to its velocity

c) is perpendicular to its velocity d) is zero



Q29 Following charge has maximum frequency of rotation in uniform transverse magnetic field :-


a) a proton

b) an alpha particle

c) an electron d) a neutron



Q30 Magnetic field is parallel to the plane of coil then torque will be :-


a) Maximum

b) Minimum

c) Zero d) None of these



Q31 Under the influence of a uniform magnetic field a charged particle is moving in a circle of radius R with constant speed v. The time period of the motion :-


a) depends on R and not on v

b) depends on v and not on R

c) depends on both R and v d) is independent of both R and v



ANSWERS


1) d

2) d

3) d

4) d

5) c

6) b

7) d

8) a

9) a

10) c

11) d

12) c

13) a

14) b

15) c

16) a

17) d

18) a

19) b

20) c

21) b

22) d

23) d

24) b

25) c

26) a

27) a

28) d

29) c

30) a

31) d


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