MCQs on Dielectrics

Dielectric is an insulating material generally used to increase the capacitance of the capacitor. They are very poor conductors of electricity. When these dielectrics are placed in an electric field, electric polarization occurs. The positive charges in the dielectric are displaced in the direction of the electric field and the negative charges are displaced in the opposite direction.

Q1: Which among the following is a dielectric?

1. Copper
2. Aluminium
3. Plastic
4. Ceramic

Answer: (d) Ceramic

Q2: How can a dielectric be converted to a conductor?

1. Compression
2. Heating
3. Expanding
4. Freezing

Answer:(b) Heating

Q3: Which of the following statements is true for a dielectric?

1. Dielectrics are superconductors at high temperature
2. Dielectrics are superconductors at low temperature
3. The cannot become superconductors
4. They have very less breakdown voltage

Answer:(b) Dielectrics are superconductors at low temperature

Q4: Dielectric materials do not have

1. Free electrons
2. Bound charge
3. Proton
4. neutron

Answer: (a) Free electrons

Q5: Dielectric materials are basically

1. Insulators
2. Semiconductors
3. Superconductors
4. conductors

Answer: (a) insulators

Q6: Find the dielectric constant for material with electric susceptibility of 5

1. 4
2. 6
3. 7
4. 3

Answer: (b) 6

Q7: When the air in a capacitor is replaced by a medium of dielectric constant K, the capacity

1. Deceases K times
2. Increases K times
3. The K² times
4. Remains constant

Answer: (b) Increases K times

Q8: The dielectric constant cannot be

1. Infinity
2. 5
3. 6
4. 7

Answer: (a) Infinity

Q9: A capacitor of capacity C=10μF is connected to a constant voltage battery of 12 V. Now space between plates is filled with a liquid of dielectric constant 5. The charge that flows now from the battery to the capacitor is

1. 120 μC
2. 699 μC
3. 480 μC
4. 24 μC

Answer: (c) 480 μC

Q10: The capacitance of a parallel plate capacitor is C. If a dielectric slab of thickness equal to one-fourth of the plate separation and dielectric constant K is inserted between the plates, then the capacitance becomes

1. KC/2(K+1)
2. 2KC/K+1
3. 5KC/4K+1
4. 4KC/3K+1

Answer: (d) 4KC/3K+1

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