Page 331 - Schaum's Outline of Theory and Problems of Applied Physics

316 CAPACITANCE [CHAP. 26

Multiple-Choice Questions

26.1. The farad is not equivalent to which of the following combinations of units?
2
(a) C /J (c) CV 2
(b) C/V (d) J/V 2

26.2. The distance between the plates of a parallel-plate capacitor of capacitance C is doubled and their area is halved.
The capacitor now has a capacitance of
(a) C/4 (c) 2C
(b) C (d) 4C

26.3. A parallel-plate capacitor with air between its plates has an energy of W when it is charged until a potential difference
of V appears across its plates. An otherwise identical capacitor has a material of dielectric constant K = 2 between
its plates and is also charged to the potential difference V. The energy of the second capacitor is
(a) W/2 (c) 2W
(b) W (d) 4W

26.4. A capacitor connected to a 24-V battery has a charge of 0.004 C. Its capacitance is
(a) 1.67 µF (c) 167 µF
(b) 60 µF (d) 0.048 F

26.5. The capacitance of a parallel-plate capacitor is 20 µF in air and 42 µF when Teflon is between its plates. Teflon has
a dielectric constant of
(a) 0.48 (c) 2.1
(b) 1.4 (d) 4.2

26.6. The equivalent resistance of two 20-µF capacitors in series is
(a) 0.1 µF (c) 30 µF
(b) 10 µF (d) 40 µF

26.7. The capacitor combination in Question 26.6 is connected across a 100-V battery. The potential difference across
each capacitor is

(a) 25 V (c) 100 V
(b) 50 V (d) 200 V

26.8. The equivalent resistance of two 20-µF capacitors in parallel is
(a) 0.1 µF (c) 30 µF
(b) 10 µF (d) 40 µF

26.9. The capacitor combination in Question 26.7 is connected across a 100-V battery. The potential difference across
each capacitor is
(a) 25 V (c) 100 V
(b) 50 V (d) 200 V

26.10. A charged 50-µF capacitor has an energy of 1 J. The voltage across it is
(a) 141 V (c)20 kV
(b) 200 V (d)40 kV