JEE Physics Magnetism and Matter MCQs Set B

Question: Two different magnets are tied together and allowed to vibrate in a horizontal plane. When their like poles are joined, time period of oscillation is 5 s and with unlike poles joined, time period of oscillation is 15 s. The ratio of their magnetic moments is

• a) 5 : 4
• b) 1 : 3
• c) 3 : 1
• d) 2 : 5

Answer: 5 : 4

Question: The values of the apparent angles of dip in two planes at right angles to each other are 45° and 30° respectively. The true value of angle of dip at the place is

• a) cot^–1 (2)
• b) cot^–1 (1)
• c) cot^–1 (3)
• d) cot^–1 (4)

Answer: cot^–1 (2)

Question: A magnet is placed horizontally on ground with its north pole towards the geographic north pole of the earth. The neutral point is obtained

• a) On the east-west line through the centre of the magnet
• b) In only east side of the magnet
• c) In only west side of the magnet
• d) Along the axis of the magnet

Answer: On the east-west line through the centre of the magnet

Question: The value of horizontal component of earth’s magnetic field at a place is 0.35 × 10^–4 T. If the angle of dip is 60°, the value of vertical component of earth’s magnetic field is nearly

• a) 0.61 × 10^–4 T
• b) 0.4 × 10^–4 T
• c) 0.2 × 10^–4 T
• d) 0.1 × 10^–4 T

Answer: 0.61 × 10^–4 T

Question: The period of oscillation of a magnet of a vibration magnetometer is 2.45 s at one place and 4.9 s at the other. The ratio of the horizontal component of earth magnetic field at the two places is

• a) 4 : 1
• b) 2 : 1
• c) 1 : 2
• d) 1 : 4

Answer: 4 : 1

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: A tangent galvanometer has 80 turns of wire. The internal and external diameters of the coil are 19 cm and 21 cm respectively. The reduction factor of the galvanometer at a place where H = 0.32 oersted will be (1 oersted = 80 A/m)

• a) 0.064
• b) None of these
• c) 0.64
• d) 0.0064

Answer: 0.064

Question: Magnetic susceptibility for a diamagnetic substance is

• a) Small and negative
• b) Small and positive
• c) Large and negative
• d) Large and positive

Answer: Small and negative

Question:  Area of B-H curve measures the energy loss

• a) Per unit volume per cycle of the specimen
• b) By the specimen
• c) Per unit volume of the specimen
• d) Per cycle of the specimen

Answer: Per unit volume per cycle of the specimen

Question:  A wire of length l m carrying a current I ampere, is bent in the form of a circle. The magnetic moment is

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: Bohr magneton is given by (symbols have their usual meanings)

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: The unit of magnetic susceptibility is

• a) Dimensionless
• b) henry
• c) weber per metre
• d) weber

Answer: Dimensionless

Question: One weber is equal to

• a) 10⁸ maxwell
• b) 10⁶ maxwell
• c) 10⁴ maxwell
• d) 10² maxwell

Answer: 10⁸ maxwell

Question: If the number of turns and radius of cross section of the coil of a tangent galvanometer are doubled, then the reduction factor K will become

• a) K
• b) 2K
• c) 4K
• d)

  

Answer: K

Question: Two short bar magnets of magnetic moments 'M' each are arranged at the opposite corners of a square of side 'd', such that their centres coincide with the corners and their axes are parallel to one side of the square. If the like poles are in the same direction, the magnetic induction at any of the other corners of the square is

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:

• a) 2
• b) 1
• c) 3
• d) 4

Answer:  2

Question:

• a) 2M
• b) M
• c) Zero
• d)

  

Answer: 2M

Question:

• a)

  

• b)

  

• c)

  

• d) Zero

Answer:

Question: The work done in rotating a bar magnet of magnetic moment M from its unstable equilibrium position to its stable equilibrium position in a uniform magnetic field B is

• a) –2MB
• b) –MB
• c) MB
• d) 2MB

Answer: –2MB

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:

• a) Zero
• b) Directed along OP
• c) Directed perpendicular to the plane of paper
• d) Directed along PO

Answer: Zero

Question:

• a) 3 J
• b)

  

• c)

  

• d)

  

Answer: 3 J

Question:

• a) 6 J
• b) 12 J
• c) 12 J
• d) 2 J

Answer: 6 J

Question: A short bar magnet of magnetic moment 0.4 JT^–1 is placed in a uniform magnetic field of 0.16 T. The magnet is in stable equilibrium when the potential energy is

• a) – 0.064 J
• b) Zero0.064 J
• c) 0.064 J
• d) – 0.082 J

Answer: – 0.064 J

Question: A magnet oscillates, in earth’s magnetic field, with a time-period T. If its mass is quadrupled, then its new time-period will be

• a) 2T, motion remaining S.H.M.
• b) Unaffected but motion is not S.H.M.
• c)

  

• d) 4T, motion remaining S.H.M.

Answer: 2T, motion remaining S.H.M.

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: Tangent galvanometer is used to measure

• a) Current
• b) Charge
• c) Potential difference
• d) Resistance

Answer: Current

Question: The magnetic moment of a diamagnetic atom is

• a) Equal to zero
• b) Equal to one
• c) Much greater than one
• d) Between zero and one

Answer: Equal to zero

Question: The work done in turning a magnet of magnetic moment M by an angle of 90° from the magnetic meridian is n times the corresponding work done to turn it through an angle of 60°. The value of n is

• a) 2
• b) 1
• c)

  

• d)

  

Answer: 2

Question: A compass needle which is allowed to move in a horizontal plane is taken to a geomagnetic pole. It

• a) Will stay in any position
• b) Will stay in east-west direction only
• c) Will stay in north-south direction only
• d) Will become rigid showing no movement

Answer: Will stay in any position

Question: Due to earth’s magnetic field, the charged cosmic rays particles

• a) Can never reach the equator
• b) Can never reach the pole
• c) Require greater kinetic energy to reach the equator than pole
• d) Require less kinetic energy to reach the equator than pole

Answer: Can never reach the equator

Question: There are four light-weight-rod samples, A, B, C, D separately suspended by threads. A bar magnet is slowly brought near each sample and the following observations are noted

(i) A is feebly repelled
(ii) B is feebly attracted
(iii) C is strongly attracted
(iv) D remains unaffected
Which one of the following is true?

• a) B is of a paramagnetic material
• b) D is of a ferromagnetic material
• c) A is of a non-magnetic material
• d) C is of a diamagnetic material

Answer: B is of a paramagnetic material

Question: Curie temperature is the temperature above which

• a) Ferromagnetic material becomes paramagnetic material
• b) Ferromagnetic material becomes diamagnetic material
• c) Paramagnetic material becomes diamagnetic material
• d) Paramagnetic material becomes ferromagnetic material

Answer: Ferromagnetic material becomes paramagnetic material

Question: For protecting a sensitive equipment from the external magnetic field, it should be

• a) Placed inside an iron can
• b) Surrounded with fine copper sheet
• c) Wrapped with insulation around it when passing current through it
• d) Placed inside an aluminium can

Answer: Placed inside an iron can

Question: If a diamagnetic substance is brought near north or south pole of a bar magnet, it is

• a) Repelled by the poles
• b) Repelled by north pole and attracted by the south pole
• c) Attracted by the poles
• d) Attracted by the north pole and repelled by the south pole

Answer: Repelled by the poles

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: According to Curie’s law, the magnetic susceptibility of a substance at an absolute temperature T is proportional to

• a)

  

• b)

  

• c)

  

• d) T

Answer:

Question: A diamagnetic material in a magnetic field moves

• a) From stronger to the weaker parts of the field
• b) Perpendicular to the field
• c) From weaker to the stronger parts of the field
• d) In none of the above directions

Answer: From stronger to the weaker parts of the field

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: Nickel shows ferromagnetic property at room temperature. If the temperature is increased beyond Curie temperature, then it will show

• a) Paramagnetism
• b) Diamagnetism
• c) No magnetic property
• d) Anti ferromagnetism

Answer: Paramagnetism

Question:  Electromagnets are made of soft iron because soft iron has

• a) Low retentivity and low coercive force
• b) Low retentivity and high coercive force
• c) High retentivity and low coercive force
• d) High retentivity and high coercive force

Answer: Low retentivity and low coercive force

Question: A current loop in a magnetic field

• a) Can be in equilibrium in two orientations, one stable while the other is unstable
• b) Experience a torque whether the field is uniform or non-uniform in all orientations
• c) Can be in equilibrium in two orientations, both the equilibrium states are unstable
• d) Can be in equilibrium in one orientation

Answer: Can be in equilibrium in two orientations, one stable while the other is unstable

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:

• a)

  

• b)

  

• c)

  

• d) M

Answer:

Question: An iron nail near a bar magnet experiences

• a) Torque and force of attraction
• b) Torque and force of repulsion
• c) Only torque
• d) Only force

Answer: Torque and force of attraction