11. A substance whose permeability is less than the permeability of free space is?
A. Diamagnetic
B. Paramagnetic
C. Ferromagnetic
D. Not a magnetic substance
Answer: A
A diamagnetic material creates a magnetic field opposing that of the external magnetic field and it repels the external magnetic field. Hence its permeability is less than that of free space.
13. Which among the following have negative susceptibility?
A. Diamagnetic
B. Paramagnetic
C. Ferromagnetic
D. Not a magnetic substance
Answer: A
Magnetic susceptibility is the degree of magnetization of a material in response to the external magnetic field. Diamagnetic substances repel the magnetic field and hence have negative susceptibility.
14. Which among the following have positive susceptibility?
A. Diamagnetic
B. Paramagnetic
C. Ferromagnetic
D. Both paramagnetic and ferromagnetic
Answer: D
Magnetic susceptibility is the degree of magnetization of a material in response to the external magnetic field. Both paramagnetic and ferromagnetic materials have positive susceptibility as they get magnetized when placed in an external magnetic field.
15. A substance whose permeability is more than the permeability of free space is?
A. Diamagnetic
B. Paramagnetic
C. Ferromagnetic
D. Both paramagnetic and ferromagnetic
Answer: D
A substance whose permeability is more than the permeability of free space is both paramagnetic and ferromagnetic.
Relative permeability = 1+Magnetic susceptibility
Since both paramagnetic and ferromagnetic materials have positive susceptibility, their relative permeability is greater than unity i.e. their permeability is more than the permeability of free space.
16. The unit for permeability of free space is?
A. Henry
B. Henry-m
C. Henry/m
D. Henry/m2
Answer: C
Using the formula of self-inductance of the solenoid,
L = µ0n2A/l
We get a unit of µ0 = Henry/m.
17. Which among the following is a correct expression for µ0?
A. µ0 = BH
B. µ0 = B/H
C. µ0 = H/B
D. µ0 = BH2
Answer: B
Magnetic permeability is the constant of proportionality between the magnetic flux density and magnetic field strength of a given medium. Hence µ0 = B/H.
18. Calculate the magnetic flux density if the magnetic field strength is 2A/m.
A. 4×π×10-7 T
B. 8×π×10-7 T
C. 10×π×10-7 T
D. 12×π×10-7 T
Answer: B
We know that:
µ0 = B/H
Substituting the value of H from the question, we get
B = 8×π×10-7T.
19. Calculate the magnetic field strength if the magnetic flux density is 4×πT.
A. 10-7/16×π2A/m
B. 10-7A/m
C. 107A/m
D. 10-7A
Answer: C
We know that:
µ0 = B/H
Substituting the value of B from the question, we get
H = 107A/m.
20. Calculate the magnetic flux density if the magnetic field strength is 3A/m.
A. 4×π×10-7 T
B. 8×π×10-7 T
C. 10×π×10-7 T
D. 12×π×10-7 T
Answer: D
We know that:
µ0 = B/H
Substituting the value of H from the question, we get
