Practice important
Relative Permittivity
MCQ questions and answers.
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MCQ Questions
1. The relative permittivity of a material is defined as the ratio of its permittivity to:
A.
The electric field
B.
The permittivity of free space
C.
The charge on a conductor
D.
The potential difference
Correct Answer:
The permittivity of free space
Explanation:
Relative permittivity is defined as εr = ε/ε0, where ε is the permittivity of the material and ε0 is the permittivity of free space.
2. What is the relative permittivity of free space?
A.
0
B.
1
C.
8.85
D.
9 × 10^9
Correct Answer:
1
Explanation:
The relative permittivity of free space is one because its permittivity is ε0, so εr = ε0/ε0 = 1.
3. Relative permittivity is a:
A.
Quantity with the unit farad
B.
Quantity with the unit coulomb
C.
Dimensionless quantity
D.
Quantity with the unit volt
Correct Answer:
Dimensionless quantity
Explanation:
Relative permittivity is the ratio of two quantities with the same unit, ε and ε0. Therefore, it has no unit.
4. If the permittivity of an insulator is 4ε0, its relative permittivity is:
A.
ε0
B.
2
C.
4
D.
4ε0
Correct Answer:
4
Explanation:
Using εr = ε/ε0, we get εr = 4ε0/ε0 = 4.
5. An insulating material has relative permittivity 5. Its permittivity is:
A.
ε0/5
B.
5ε0
C.
5/ε0
D.
ε0 + 5
Correct Answer:
5ε0
Explanation:
The relation ε = εrε0 gives ε = 5ε0 for a material whose relative permittivity is 5.
6. A material with higher relative permittivity has:
A.
Lower permittivity than free space
B.
The same permittivity as vacuum in every case
C.
Greater permittivity compared with free space
D.
Zero permittivity
Correct Answer:
Greater permittivity compared with free space
Explanation:
Since ε = εrε0, a relative permittivity greater than one means that the material has greater permittivity than free space.
7. A capacitor has capacitance C0 without an insulating material. When completely filled with a material of relative permittivity 3, its capacitance becomes:
A.
C0/3
B.
C0
C.
2C0
D.
3C0
Correct Answer:
3C0
Explanation:
When a dielectric completely fills a capacitor, its capacitance becomes C = εrC0. For εr = 3, C = 3C0.
8. If the relative permittivity of an insulator is 2, its permittivity is how many times the permittivity of free space?
A.
One-half
B.
One
C.
Two
D.
Four
Correct Answer:
Two
Explanation:
Relative permittivity directly gives the ratio ε/ε0. Thus, εr = 2 means the permittivity is two times ε0.
9. Which material has the greatest relative permittivity among the following?
A.
Material with εr = 1
B.
Material with εr = 2
C.
Material with εr = 4
D.
Material with εr = 3
Correct Answer:
Material with εr = 4
Explanation:
A larger value of εr represents a greater relative permittivity. Among the given values, 4 is the greatest.
10. For an insulating material with permittivity equal to the permittivity of free space, the relative permittivity is:
A.
0
B.
1
C.
2
D.
ε0
Correct Answer:
1
Explanation:
If ε = ε0, then εr = ε/ε0 = 1. Thus, the relative permittivity is one.