250+ TOP MCQs on Capacitors and Capacitance | Class12 Physics

Physics Multiple Choice Questions on “Capacitors and Capacitance”.

1. What is the dimensional formula of capacitance of a capacitor?
a) M¹L²T^-4I^-2
b) M^-1L^-2T⁴I²
c) M^-1L^-2T⁶
d) M^-2L²T⁴

Answer: b
Clarification: We know that Capacitance=Charge*(voltage)^-1
Now charge=current*time=[I¹T¹].
voltage=electric field*distance, and electric field=force*(charge)^-1
Since we know the dimensional formula of force is [M¹L¹T^-2], therefore,
Electric field=[M¹L¹T^-2] * [I¹T¹]^-1=[M¹L¹T^-3I^-1].
Finally, voltage becomes=[M¹L¹T^-3I^-1] *L.
Hence, we conclude that dimensional formula of capacitance is [I¹T¹] * ([M¹L¹T^-3I^-1] *L)^-1 that is M^-1L^-2T⁴I².

2. When ‘n’ capacitors are connected in series the total capacitance(C) of the combination is given by ______
a) C=C₁+C₂+C₃+C₄+…..+C_n
b) C=C₁*C₂*C₃*C₄*…..*C_n
c) (frac {1}{C} = frac {1}{C_1} + frac {1}{C_2} + frac {1}{C_3} + ……. + frac {1}{C_n})
d) C=(frac {(C_1+C_2+C_3+C_4+……+C_n)}{n})

Answer: c
Clarification: The equivalent capacitance of the parallel plate capacitors connected in series is given by the sum of the reciprocals of the individual capacitances. That is mathematically,
(frac {1}{C} = frac {1}{C_1} + frac {1}{C_2} + frac {1}{C_3} + ……. + frac {1}{C_n})

3. What is the value of capacitance of a capacitor if it has a charge of 9C and voltage of 5V?
a) 1.8F
b) 45F
c) 4.5F
d) 8.1F

Answer: a
Clarification: Since we know that capacitance=(frac {charge}{voltage}).
Therefore capacitance=(frac {9}{5})=1.8F.

4. The total capacitance of capacitors connected in parallel is given by _____
a) product of the individual capacitors in parallel
b) sum of all the individual capacitors in parallel
c) sum of their reciprocals
d) product of their reciprocals

Answer: b
Clarification: The equivalent capacitance of the capacitors connected in parallel is given by sum of their individual capacitances, that is if there are n capacitors in parallel the total capacitance is given by, C=C₁+C₂+C₃+C₄+…..+C_n.

5. What happens to the capacitance when a dielectric material is inserted between the plates of a parallel plate capacitor?
a) Capacitance decreases
b) Capacitance remains same
c) Capacitance increases
d) Depends upon the material of the dielectric

Answer: c
Clarification: When a dielectric material is inserted between the plates of the parallel plate capacitor, the capacitance of the capacitor increases with a factor of K. That is C=KC₀.