# Basic Electrical Engineering Questions and Answers – Permeability of Free Space or Magnetic Constant

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This set of Basic Electrical Engineering Quiz focuses on “Permeability of Free Space or Magnetic Constant”.

1. Permeability of free space is also known as _________
a) Magnetic constant
b) Electric constant
c) Electrostatic constant
d) Magnetostatic constant

Explanation: The permeability of free space is also known as the magnetic constant. The permittivity of free space is the electrostatic constant.

2. A substance whose permeability is less than the permeability of free space is?
a) Diamagnetic
b) Paramagnetic
c) Ferromagnetic
d) Not a magnetic substance

Explanation: 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.

3. Which, among the following, have negative susceptibility?
a) Diamagnetic
b) Paramagnetic
c) Ferromagnetic
d) Not a magnetic substance

Explanation: Magnetic susceptibility is the degree of magnetisation of a material in response to the external magnetic field. Diamagnetic substances repel the magnetic field and hence have negative susceptibility.
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4. Which, among the following, have positive susceptibility?
a) Diamagnetic
b) Paramagnetic
c) Ferromagnetic
d) Both paramagnetic and ferromagnetic

Explanation: Magnetic susceptibility is the degree of magnetisation of a material in response to the external magnetic field. Both paramagnetic and ferromagnetic materials have positive susceptibility as they get magnetise when placed in external magnetic field.

5. A substance whose permeability is more than the permeability of free space is?
a) Diamagnetic
b) Paramagnetic
c) Ferromagnetic
d) Both paramagnetic and ferromagnetic

Explanation: 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.

6. The unit for permeability of free space is?
a) Henry
b) Henry-m
c) Henry/m
d) Henry/m2

Explanation: Using formula of self inductance of solenoid, L=µ0n2A/l
We get unit of µ0 = Henry/m.

7. Which among the following, is a correct expression for µ0.
a) µ0=BH
b) µ0=B/H
c) µ0=H/B
d) µ0=BH2

Explanation: Magnetic permeability is the constant of proportionality between the magnetic flux density and magnetic field strength of a given medium. Hence µ0=B/H.

8. Calculate the magnetic flux density if the magnetic field strength is 2A/m.
a) 4*pi*10-7T
b) 8*pi*10-7T
c) 10*pi*10-7T
d) 12*pi*10-7T

Explanation: We know that:
µ0=B/H
Substituting the value of H from the question, we get B = 8*pi*10-7T.

9. Calculate the magnetic field strength if the magnetic flux density is 4*piT.
a) 10-7/16*pi2A/m
b) 10-7A/m
c) 107A/m
d) 10-7A

Explanation: We know that:
µ0=B/H
Substituting the value of B from the question, we get H = 107A/m.

10. Calculate the magnetic flux density if the magnetic field strength is 3A/m.
a) 4*pi*10-7T
b) 8*pi*10-7T
c) 10*pi*10-7T
d) 12*pi*10-7T

Explanation: We know that:
µ0=B/H
Substituting the value of H from the question, we get B = 12*pi*10-7T.

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