NEET Physics Magnetism and Matter MCQs Set A

a)

b) is pointing radially outwards

c)

d)

Answer:

Question: The magnetic field of the earth can be modelled by that of a point dipole placed at the centre of the earth. The dipole axis makes an angle of 11.3° with the axis of the earth. At Mumbai, declination is nearly zero. Then,

a) the declination varies between 11.3° W to 11.3° E

b) the least declination is 0°

c) the plane defined by dipole axis and the earth axis passes through Greenwich

d) declination averaged over the earth must be always negative

Answer: the declination varies between 11.3° W to 11.3° E

Question: In a permanent magnet at room temperature

a) domains are all perfectly aligned

b) the individual molecules have non-zero magnetic moment which are all perfectly aligned

c) domains are partially aligned

d) magnetic moment of each molecule is zero

Answer:  domains are all perfectly aligned

Question: Magnetic lines of force due to a bar magnet do not intersect because

a) a point always has a single net magnetic field

b) the lines have similar charges and so repel each other

c) the lines always diverge from a single force

d) the lines need magnetic lenses to be made to interest

Answer: a point always has a single net magnetic field

Question: Assertion : The ferromagnetic substance do not obey Curie’s law.
Reason : At Curie point a ferromagnetic substance start behaving as a paramagnetic substance

a) Assertion is correct, reason is incorrect

b) Assertion is incorrect, reason is correct.

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 correct, reason is incorrect

Question:  The coercivity of a small magnet where the ferromagnet gets demagnetized is 3 × 10³ Am^–1. The current required to be passed in a solenoid of length 10 cm and number of turns 100, so that the magnet gets demagnetized when inside the solenoid, is:

a) 3 A

b) 6 A

c) 60 mA

d) 30 mA

Answer: 3 A

Question: Assertion : A paramagnetic sample display greater magnetisation (for the same magnetic field) when cooled.
Reason : The magnetisation does not depend on temperature.

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: The magnetic susceptibility is negative for

a) diamagnetic material only

b) paramagnetic material only

c) ferromagnetic material only

d) paramagnetic and ferromagnetic materials

Answer:  diamagnetic material only

Question: Two points A and B are situated at a distance x and 2x respectively from the nearer pole of a magnet 2 cm long. The ratio of magnetic field at A and B is

a) 8 : 1 approximately

b) 4 : 1 exactly

c) 4 : 1 approximately

d) 1 : 1 approximately

Answer: 8 : 1 approximately

Question: Assertion : Electromagnetic are made of soft iron.
Reason : Coercivity of soft iron is small.

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 magnetic needle of magnetic moment 6.7 × 10^–2 Am² and moment of inertia 7.5 × 10^–6 kg m² is performing simple harmonic oscillations in a magnetic field of 0.01 T. Time taken for 10 complete oscillations is :

a) 6.65 s

b) 8. 89 s

c) 8.76 s

d) 6.98 s

Answer: 6.65 s

Question: Assertion : The poles of magnet can not be separated by breaking into two pieces.
Reason : The magnetic moment will be reduced to half when a magnet is broken into two equal pieces

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 thin diamagnetic rod is placed vertically between the polesof an electromagnet. When the current in the electromagnet is switched on, then the diamagnetic rod is pushed up, out of the horizontal magnetic field. Hence the rod gains gravitational potential energy. The work required to do this comes from

a) the current source

b) the magnetic field

c) the induced electric field due to the changing magnetic field

d) the lattice structure of the material of the rod

Answer:  the current source

Question:  The given figure represents a material which is

a) diamagnetic

b) paramagnetic

c) ferromagnetic

d) none of these

Answer: diamagnetic

Question: Assertion : The earths magnetic field is due to iron present in its core.
Reason : At a high temperature magnet losses its magnetism

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