Moving Charges And Magnetism Mock Test

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Quiz: Moving Charges and Magnetism – Progressive Test
Total questions: 360
Questions in this round: 50
Time allotted: 70 minutes
Pass score: 60%
Total rounds: 8
Current round: 1^st
Rounds passed: 0 / 8
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Quiz: Moving Charges and Magnetism – Certificate Challenge
Total questions: 360
Questions to attempt: 100 random
Time allotted: 100 minutes
Certificate pass score: 70%
Random questions: Yes
Certificate: Yes
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Progressive Test — Guest First Round

Moving Charges and Magnetism – Progressive Test

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1 / 50

1. A long straight wire carries current . The magnetic field at a distance from it has magnitude

2 / 50

2. A magnetic field acts on two particles moving with the same speed at the same angle to . Particle P has charge , and particle Q has charge , with equal masses. Comparing the magnetic forces at entry,

a) both magnitude and direction are identical

b) the magnitudes are unequal and the directions are the same

c) both forces are zero because charges cancel each other

d) the magnitudes are equal and the directions are opposite

3 / 50

3. The SI unit of magnetic dipole moment of a current loop is

4 / 50

4. In the Ampere-law derivation of the magnetic field inside a long solenoid, a rectangular Amperian loop is chosen with one long side inside the solenoid and one long side outside. The outside contribution is neglected because

a) outside field is nearly zero

b) inside field is transverse

c) outside current is zero

d) outside field lines are open

5 / 50

5. The electric part and magnetic part of the Lorentz force differ in an important way. The electric force

a) exists only when

b) has direction independent of charge sign

c) is always perpendicular to velocity

d) can act on a stationary charge

6 / 50

6. The magnetic field on the axis of a single circular current loop of radius , at a distance from its centre, is

7 / 50

7. The quantity in the magnetic force relation for a straight current-carrying conductor represents

a) along conventional current, with magnitude

b) opposite conventional current, with magnitude

c) normal to the conductor surface, with magnitude

d) along the magnetic field, with magnitude

8 / 50

8. The torque on a magnetic dipole moment in a uniform magnetic field is represented by

9 / 50

9. A current loop of area is placed in a magnetic field . Its plane makes an angle with . The torque magnitude is

d) zero for every

10 / 50

10. Study the table for two long parallel wires carrying currents and .

Row	Current directions	Magnetic force
P	Same direction	Attractive
Q	Opposite directions	Repulsive
R	Same direction	Force per unit length
S	Opposite directions	Attractive

The row that contains an incorrect statement is

a) Row R

b) Row Q

c) Row S

d) Row P

11 / 50

11. The instantaneous power delivered by magnetic force on a moving charge is

12 / 50

12. Study the table about field roles in a cyclotron.

Row	Part of cyclotron	Main role
P	Magnetic field in the dees	Bends the path into circular arcs
Q	Electric field across the gap	Accelerates the charged particle
R	Alternating oscillator	Maintains proper timing of acceleration
S	Magnetic field inside the dees	Directly increases kinetic energy by doing work

The row that gives an incorrect role is

a) Row R

b) Row Q

c) Row P

d) Row S

13 / 50

13. For a circular loop carrying current , let be the magnetic field at its centre. At an axial point where , the magnetic field is

14 / 50

14. A proton enters a region of uniform magnetic field with velocity perpendicular to . The magnetic force is directed

a) perpendicular to and

b) parallel to and not to

c) parallel to and not to

d) opposite to and not to

15 / 50

15. If the separation between two long parallel wires is doubled while both currents remain unchanged, the force per unit length becomes

a) unchanged

b) one-fourth of its earlier value

c) half of its earlier value

d) twice its earlier value

16 / 50

16. For a non-relativistic charged particle in a cyclotron, the cyclotron frequency is

17 / 50

17. A wire of length carries a current of in a magnetic field of . The angle between the wire and the field is . The force on the wire is

18 / 50

18. Use the graph description below.

A graph of axial magnetic field of a circular current loop is plotted against axial distance from the centre. The current and radius are fixed, and both positive and negative values of are considered.

The graph is symmetric about because

a) depends on in the axial-field expression

b) current changes direction on the two sides of the loop

c) the field becomes zero at the centre

d) depends directly on only

19 / 50

19. Study the table about galvanometer conversion formulas.

Row	Conversion	Added resistance
P	Ammeter of range	in parallel
Q	Voltmeter of range	in series
R	Ammeter of range	in series
S	Voltmeter of range	Effective resistance is large

The row that wrongly matches the conversion is

a) Row S

b) Row P

c) Row Q

d) Row R

20 / 50

20. A charged particle enters a uniform magnetic field with fixed speed at an angle to . If is increased from to , the radius of the helical path changes by the factor

21 / 50

21. A coil has turns, area , and carries current . It is placed in a uniform magnetic field of with its area vector perpendicular to the field. The torque on the coil is

22 / 50

22. Two long parallel wires P and Q are placed horizontally. P carries current to the right and Q carries current to the left. The magnetic interaction between them is

a) repulsion, because the currents are in opposite directions

b) attraction, because both wires contain moving charges

c) attraction, because the currents are parallel to the wires

d) zero, because the wires are horizontal

23 / 50

23. A closed path is chosen near a long straight wire, but the wire lies outside the closed path. For that path, Ampere’s law gives

a) at every point of the path

24 / 50

24. A voltmeter is made by adding a series resistance to a galvanometer. If the added resistance is smaller than the required value for a given voltage range, the voltmeter will

a) draw more than and over-deflect

b) draw exactly zero current

c) automatically become an ammeter

d) become an ideal voltmeter

25 / 50

25. At a point on the axis of a circular current loop, the magnetic field is maximum when the point is

a) at , the centre of the loop

b) at , one radius from centre

c) at , two radii from centre

d) at very large on the axis

26 / 50

26. A positive ion moves to the right between crossed fields. The electric field is upward, and the ion is observed to move undeflected. The magnetic force on the ion must be

a) to the right

b) opposite to its velocity

c) upward

d) downward

27 / 50

27. A region has magnetic field lines drawn very close together near point P and widely separated near point Q. The best interpretation is that

a) is stronger near P than near Q

b) field-line spacing has no relation to field strength

c) is zero near P

d) is weaker near P than near Q

28 / 50

28. The magnetic force on a moving charge is zero in both parallel and anti-parallel motion because

b) the charge becomes neutral in both cases

d) the magnetic field cancels the electric field automatically

29 / 50

29. A loudspeaker is often mentioned with motors and galvanometers because its basic working also involves

a) heating of a conductor without magnetic interaction

b) magnetic force on a current-carrying coil

c) reflection of sound from a rigid wall

d) electrostatic force between two fixed charges only

30 / 50

30. A charged particle moves in a circular path under a uniform magnetic field with constant speed. Its acceleration is non-zero because

a) velocity changes direction continuously

b) kinetic energy increases continuously

c) magnetic force acts parallel to velocity

d) acceleration depends only on change in speed

31 / 50

31. In the non-relativistic operation of a cyclotron, the particle moves in spirals of increasing radius. The radius increases mainly because

a) electric field at the gap increasing speed

b) mass decreasing after each crossing

c) charge magnitude increasing after each turn

d) magnetic field doing work inside the dee

32 / 50

32. A magnetic-relations sheet lists the following pairs.

Row	Situation	Useful relation
P	Velocity selector
Q	Long solenoid interior
R	Long straight wire field
S	Magnetic field doing work on a charge

The row that should be removed from the relation sheet is

a) Row P

b) Row Q

c) Row R

d) Row S

33 / 50

33. A magnetic dipole of moment is placed in a uniform magnetic field of . The increase in potential energy when it is turned from to is

34 / 50

34. Two long parallel wires carry currents and in the same direction. At the position of wire , the magnetic field due to wire is perpendicular to wire . The force per unit length on wire is obtained from

35 / 50

35. Study the table for a straight current-carrying conductor in a uniform magnetic field.

Row	Change made	Effect on force magnitude
P	doubled	doubles
Q	doubled	doubles
R	doubled	doubles
S	changed from to	doubles

The row that contains an incorrect effect is

a) Row Q

b) Row P

c) Row S

d) Row R

36 / 50

36. A voltmeter made from a galvanometer has range and total resistance . The full-scale galvanometer current is

37 / 50

37. A galvanometer has and . It is converted into an ammeter using a shunt . The full-scale range of the ammeter is

38 / 50

38. Assertion: A current loop in a uniform magnetic field can have zero net force but non-zero torque.
Reason: Forces on opposite sides may cancel in translation while forming a couple.

a) Both Assertion and Reason are true, and Reason explains Assertion

b) Assertion is false, but Reason is true

c) Assertion is true, but Reason is false

d) Both Assertion and Reason are true, but Reason does not explain Assertion

39 / 50

39. A galvanometer has and full-scale current . A shunt of is connected. The approximate ammeter range is

40 / 50

40. A proposed solution says: “A closed current loop in a uniform magnetic field has zero net force, so it cannot have torque.” The error in this claim is that

a) a closed loop always has non-zero net force in a uniform field

b) zero net force does not rule out a couple producing torque

c) torque requires net force to be non-zero in every situation

d) magnetic forces on the sides of a loop are always zero

41 / 50

41. Use the graph description below.

For two long parallel wires carrying fixed currents and , a graph of force per unit length against is drawn, where is the separation between the wires.

The slope of this graph is

42 / 50

42. A current element produces at a point. If the current is doubled and the distance of the point from the element is also doubled, with and unchanged, the new magnetic field contribution is

43 / 50

43. Three long parallel wires are perpendicular to the page. Wire P carries out of the page, wire Q carries out of the page, and wire R carries into the page. Q is midway between P and R, with equal separation from each. The net force on wire Q is

a) perpendicular to the line joining P and R

b) toward P

c) zero

d) toward R

44 / 50

44. Read the two statements below.
I. A magnetic field can exert force on a moving charge.
II. A magnetic field always changes the speed of a charged particle.
For motion under magnetic field alone, the best evaluation is

a) I is false and II is true

b) I is true and II is true

c) I is true and II is false

d) I is false and II is false

45 / 50

45. A current loop has its plane perpendicular to a uniform magnetic field. The torque on it is zero because

a) area vector is perpendicular to

b) every side has zero magnetic force

c) current in the loop becomes zero

d) area vector is parallel to the field

46 / 50

46. The magnetic field contribution due to a small current element is described by the Biot-Savart law. Its vector form is

47 / 50

47. To convert a galvanometer into a voltmeter of range , a resistance is connected in series. The purpose of this series resistance is to

a) make the effective resistance very small

b) bypass the galvanometer current completely

c) limit current to at full-scale voltage

d) place most voltage across a parallel shunt

48 / 50

48. A circular loop carries current clockwise as seen from the right side of its axis. The magnetic field at the centre, as seen from that right side, is directed

a) away from the observer

b) toward the observer

c) radially outward in the plane of the loop

d) along the tangent to the loop

49 / 50

49. A galvanometer of resistance and full-scale current is converted into a voltmeter of range . The required series resistance is

50 / 50

50. A circular loop of radius carries current . At a point on the axis, the magnetic field is half of the field at the centre. The axial distance satisfies

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Moving Charges and Magnetism Mock Test – Class 12 Physics

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Moving Charges and Magnetism – Progressive Test

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