Physics Questions and Answers – Permanent Magnets and Electromagnets

«
»

This set of Physics Multiple Choice Questions & Answers (MCQs) focuses on “Permanent Magnets and Electromagnets”.

1. Which one of the following is feebly repelled by a magnet?
a) Diamagnetic materials
b) Paramagnetic materials
c) Ferromagnetic materials
d) Ferrimagetic materials
View Answer

Answer: a
Explanation: Diamagnetic materials are those which when placed in a magnetizing field are feebly magnetized in a direction opposite to that of the magnetizing field. Therefore, it is feebly repelled by a magnet. Example: zinc, gold, etc.
advertisement

2. Which one of the following, when suspended freely, slowly sets itself parallel to the direction of the magnetic field?
a) Ferromagnetic materials
b) Diamagnetic materials
c) Paramagnetic materials
d) Ferrimagnetic materials
View Answer

Answer: c
Explanation: Paramagnetic materials are those when suspended freely inside the magnetic field, it slowly sets itself parallel to the direction of the magnetic field. When placed in a non-uniform magnetic field, it tends to move from weaker to a stronger magnetic field.

3. Which among the following has a relative permeability much larger than 1?
a) Diamagnetic materials
b) Ferromagnetic materials
c) Paramagnetic materials
d) Ferrimagnetic materials
View Answer

Answer: b
Explanation: The relative permeability of ferromagnetic materials is much larger than 1. Ferromagnetic substances are those, which when placed in a magnetic field are strongly magnetized in the direction of the magnetizing field, i.e., it is strongly attracted by a magnet.
advertisement
advertisement

4. Aluminum is a diamagnetic material.
a) True
b) False
View Answer

Answer: b
Explanation: No, aluminum is a paramagnetic material. Paramagnetic materials are those, which when placed in a magnetic field are feebly magnetized in the direction of the magnetizing field, i.e. it is feebly attracted by a magnet.

5. Arrange the following in the increasing order of magnetic susceptibility.
a) Paramagnetic < Diamagnetic < Ferromagnetic
b) Paramagnetic < Ferromagnetic < Diamagnetic
c) Ferromagnetic < Paramagnetic < Diamagnetic
d) Diamagnetic < Paramagnetic < Ferromagnetic
View Answer

Answer: d
Explanation: Diamagnetic materials have a small and negative value of magnetic susceptibility. Paramagnetic materials have a small and positive value of magnetic susceptibility and ferromagnetic materials have a large and positive value of magnetic susceptibility.
advertisement

6. Identify the expression for Curie’s constant from the following.
a) χm = C × T
b) χm = C × 2T
c) χm = \(\frac {C}{T}\)
d) χm = \(\frac {C}{2T}\)
View Answer

Answer: c
Explanation: Curie’s law in magnetism states that the magnetic susceptibility of paramagnetic materials is inversely proportional to its absolute temperature and it is given by:
χm = \(\frac {C}{T}\)

7. Pick out the temperature at which iron becomes paramagnetic?
a) 800 °C
b) 700 °C
c) 600 °C
d) 500 °C
View Answer

Answer: a
Explanation: Iron is a ferromagnetic material. Ferromagnetism decreases with a rise in temperature, and above a certain temperature called “Curie’s temperature,” ferromagnets become paramagnets. For iron, it is approximately, 800 °C.
advertisement

8. Soft iron is used in the cores of transformers.
a) True
b) False
View Answer

Answer: a
Explanation: Soft iron has high permeability and low retentivity and is used as an electromagnet. The area under the hysteresis loop for soft iron is less. So where the repeated cycles of magnetization occur, there on using soft iron core, energy losses are less. That is why soft iron is used in cores of transformers, galvanometers, generators, etc.

9. Pick out the material that cannot be used to make permanent magnets.
a) Copper
b) Aluminum
c) Steel
d) Zinc
View Answer

Answer: d
Explanation: Permanent magnets are made up of materials having high retentivity, high coercivity, and high permeability such as steel. Other suitable materials for making permanent magnets are alnico (an alloy of iron, aluminum, nickel, copper, and cobalt), cobalt steel, and ticonal. That leaves zinc as the one that cannot be used to make permanent magnets.
advertisement

10. Find the true statement.
a) Most of the substances show ferromagnetism
b) The magnetic susceptibility of diamagnetic substances are temperature independent
c) Water is paramagnetic in nature
d) Typical domain size of a ferromagnetic material is 1 nm
View Answer

Answer: b
Explanation: The magnetic susceptibility of diamagnetic materials doesn’t depend upon temperature. This is often because there’s an outsized barrier between the bottom state and therefore the excited states of diamagnetic substances. Hence, it remains constant during the change of temperature. All the other statements are false.

Sanfoundry Global Education & Learning Series – Physics – Class 12.

To practice all areas of Physics, here is complete set of 1000+ Multiple Choice Questions and Answers.

Participate in the Sanfoundry Certification contest to get free Certificate of Merit. Join our social networks below and stay updated with latest contests, videos, internships and jobs!

advertisement
advertisement
Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He is Linux Kernel Developer & SAN Architect and is passionate about competency developments in these areas. He lives in Bangalore and delivers focused training sessions to IT professionals in Linux Kernel, Linux Debugging, Linux Device Drivers, Linux Networking, Linux Storage, Advanced C Programming, SAN Storage Technologies, SCSI Internals & Storage Protocols such as iSCSI & Fiber Channel. Stay connected with him @ LinkedIn | Youtube | Instagram | Facebook | Twitter