Electrostatic Potential and Capacitance Questions and Answers Part-18

1. The condensers of capacity \[C_{1}\]  and \[C_{2}\]  are connected in parallel, then the equivalent capacitance is
a) \[C_{1} + C_{2}\]
b) \[\frac{C_{1}C_{2}}{C_{1}+C_{2}}\]
c) \[\frac{C_{1}}{C_{2}}\]
d) \[\frac{C_{2}}{C_{1}}\]

Answer: a
Explanation: \[C_{1} + C_{2}\]

2. A parallel plate capacitor is made by stacking n equally spaced plates connected alternately. If the capacitance between any two plates is C then the resultant capacitance is
a) C
b) nC
c) \[\left(n -1\right)C\]
d) \[\left(n +1\right)C\]

Answer: c
Explanation: The given arrangement becomes an arrangement of (n - 1) capacitors connected in parallel. So CR = (n - 1)C

3.Four plates of equal area A are separated by equal distances d and are arranged as shown in the figure. The equivalent capacity is
173
a) \[\frac{2\epsilon_{0}A}{d}\]
b) \[\frac{3\epsilon_{0}A}{d}\]
c) \[\frac{5\epsilon_{0}A}{d}\]
d) \[\frac{\epsilon_{0}A}{d}\]

Answer: a
Explanation:
q173

4.The capacitor of capacitance \[4\mu F\]   and \[6\mu F\]   are connected in series. A potential difference of 500 volts applied to the outer plates of the two capacitor system. Then the charge on each capacitor is numerically
a) 6000 C
b) 1200 C
c) 1200 \[\mu C\]
d) 6000 \[\mu C\]

Answer: c
Explanation:
q174

5. A parallel plate capacitor with air as medium between the plates has a capacitance of 10 \[\mu F\]   . The area of capacitor is divided into two equal halves and filled with two media as shown in the figure having dielectric constant \[k_{1}=2\]  and \[k_{2}=4\]  . The capacitance of the system will now be
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a) 10 \[\mu F\]
b) 20 \[\mu F\]
c) 30 \[\mu F\]
d) 40 \[\mu F\]

Answer: c
Explanation:
q175

6.Three capacitors are connected to D.C source of 100 volts shown in the adjoining figure. If the charge accumulated on plates of \[C_{1},C_{2}\]   and \[C_{3}\] are \[q_{a},q_{b},q_{c},q_{d},q_{e}\]     and \[q_{f}\]   respectively, then
176a
a) \[q_{b}+q_{d}+q_{f}=\frac{100}{9}C\]
b) \[q_{b}+q_{d}+q_{f}=0\]
c) \[q_{b}+q_{d}+q_{f}=50 C\]
d) \[q_{b}=q_{d}=q_{f}\]

Answer: d
Explanation: In series combination, charge is same on each capacitor.

7. n identical condensers are joined in parallel and are charged to potential V . Now they are separated and joined in series. Then the total energy and potential difference of the combination will be
a) Energy and potential difference remain same
b) Energy remains same and potential difference is nV
c) Energy increases n times and potential difference is nV
d) Energy increases n times and potential difference remains same

Answer: b
Explanation:
q177

8. Three capacitors each of capacitance \[1\mu F\]  are connected in parallel. To this combination, a fourth capacitor of capacitance \[1\mu F\]  is connected in series. The resultant capacitance of the system is
a) \[4\mu F\]
b) \[2\mu F\]
c) \[\frac{4}{3}\mu F\]
d) \[\frac{3}{4}\mu F\]

Answer: d
Explanation:
q178

9. Five capacitors of \[10\mu F\]  capacity each are connected to a d.c. potential of 100 volts as shown in the adjoining figure. The equivalent capacitance between the points A and B will be equal to
179a
a) 40 \[\mu F\]
b) 20 \[\mu F\]
c) 30 \[\mu F\]
d) 10 \[\mu F\]

Answer: d
Explanation:
q179
q179a

10.Three capacitors of capacitances \[3\mu F,9\mu F\]     and \[18\mu F\]   are connected once in series and another time in parallel. The ratio of equivalent capacitance in the two cases \[\left(\frac{C_{s}}{C_{p}}\right)\]   will
a) 1 : 15
b) 15 : 1
c) 1 : 1
d) 1 : 3

Answer: a
Explanation:
q180