This set of Class 12 Physics Chapter 2 Multiple Choice Questions & Answers (MCQs) focuses 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
View Answer
Explanation: 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+…..+Cn
b) C=C1*C2*C3*C4*…..*Cn
c) \(\frac {1}{C} = \frac {1}{C_1} + \frac {1}{C_2} + \frac {1}{C_3} + ……. + \frac {1}{C_n}\)
d) C=\(\frac {(C_1+C_2+C_3+C_4+……+C_n)}{n}\)
View Answer
Explanation: 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
View Answer
Explanation: 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
View Answer
Explanation: 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+…..+Cn.
5. What is the total charge on the parallel plate capacitor shown?
a) 2Q
b) \(\frac {Q}{2}\)
c) 0
d) \(\frac {-Q}{2}\)
View Answer
Explanation: Since the total charge on a capacitor is given by sum of the charges on the two parallel plates, here charge on each plate is equal and opposite, hence –Q+Q=0. Therefore, the total charge on the capacitor is 0.
6. 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
View Answer
Explanation: 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.
Sanfoundry Global Education & Learning Series – Physics – Class 12.
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