Capacitor and Capacitance questions and answers for first year (first semester and second semester) basic physics or applied physics course. This chapter is included in all engineering branches (civil, electrical, mechanical, mining, computer science, information technology, metallurgical etc.) of B. Tech, B.E and polytechnic (diploma engineering) for the physics course. Multiple choice questions (MCQs), numerical and short answer type questions on capacitor for engineering physics are discussed in this article to help students.
Multiple choice questions and answers on Capacitor and Capacitance-For engineering physics course
1. The unit of capacitance is
a. Picofarad
b. coulomb
c. microvolt
d. oersted
option a
2. Capacitor is a device used to__________
a. store electrical energy
b. vary the resistance
c. store magnetic energy
d. dissipate energy
option a
3. 1 farad = _______ statfarad
a. 9×1011
b. 9×1010
c. 9×1012
d. 9×1010
option a
4. Which of the following is a passive device?
a. Transistor
b. Rectifier
c. Capacitor
d. Vacuum Tubes
option C
5. What is the value of capacitance of a capacitor which has a voltage of 4V and has 16C of charge?
a. 2F
b. 4F
c. 6F
d. 8F
option b
Charge of the capacitor, Q = 16 C
Potential difference between the two plates, V = 4 volt
From the relation, Q = CV
C = Q/V = 16/4 = 4 F
6. The capacitance between two plates increases with
a. Shorter plate area and higher applied voltage
b. Shorter play area and shorter distance between them
c. Larger plate area, longer distance between plates and higher applied voltage
d. Larger plate area and shorter distance between plates
option d
7. The capacitance of 1 μF equals
a. 10 -12 F
b. 10-8 F
c. 10-4 F
d. 10-6 F
option d
8. The capacitance of a parallel plate capacitor is
a. C=\frac{\epsilon _{0}d}{A}
b. C=\frac{\epsilon _{0}A}{d}
c. C=\frac{\epsilon _{0}}{Ad}
d. C=\frac{A}{\epsilon _{0}d}
option b
9. The equivalent capacitance of two capacitor in series is
a. C_{1}+C_{2}
b. \frac{C_{1}+C_{2}}{C_{1}C_{2}}
c. \frac{C_{1}C_{2}}{C_{1}+C_{2}}
d. None of the above
option c
Numerical questions and answer on Capacitor and Capacitance for Engineering Physics
1. Determine the amount of charge stored on either plate of a capacitor (4 µF) when connected across a 12 V battery.
Capacitance C = 4µF =4✖10-6F
Potential difference, V=12 volt
Charge, Q = CV = 4✖10-6 ✖ 12 = 4.8✖10-5C
2. A parallel plate capacitor is constructed from of metal plates, each with an area of 0.2 m2. The capacitance is 7.9 nF. Determine the plate separation distance.
Area of the metal plate, A = 0.2 m2
Capacitance, C= 7.9 nF =7.9×10-9 F
Let d be the separation between the plates, then
C=\frac{\epsilon _{0}A}{d}
d=\frac{\epsilon _{0}A}{C}
d=\frac{8.85\times 10^{-12}\times 0.2}{7.9\times 10^{-9}}
d= 0.224✖10-3 m = 0.224 mm
3. The capacity of a parallel plate condenser is 10 µF when the distance between its plates is 8 cm. If the distance between the plates is reduced to 4 cm then the capacity of this parallel plate condenser will be
a. 5 µF
b. 10 µF
c. 20 µF
d. 40 µF
option c
Capacitance, C=10 µF
distance between the two plates, d = 8 cm
Therefore, C=10 µF = \frac{\epsilon _{0}A}{d}
C=10 µF = \frac{\epsilon _{0}A}{8}
Now, the distance is 4 cm
So, capacitance will be
C'=\frac{\epsilon _{0}A}{4}
C'=2\times\frac{\epsilon _{0}A}{8}
C’ = 2✖C = 2C = 2✖10 µF=20 µF
4. A parallel plate condenser with oil between the plates (dielectric constant of oil K=2) has a capacitance C. If the oil is removed then capacitance of the capacitor becomes
a. \sqrt{2C}
b. \frac{C}{\sqrt{2}}
c. 2C
d. C/2
option d
C=\frac{K\epsilon _{0}A}{d}
C=\frac{2\epsilon _{0}A}{d}
If the oil is removed, then the capacitance
C'=\frac{\epsilon _{0}A}{d}
C’=C/2
5. Find the equivalent capacitance between the points A and B
The capacitors c/2 and C are in parallel.
So equivalent of these two capacitors is C+C/2 = 3C/2
Now, three capacitors C, 3C/2 and C are in series.
So, the equivalent of these three is C’
\frac{1}{C'}=\frac{1}{C}+\frac{2}{3C}+\frac{1}{C}
\frac{1}{C'}=\frac{8}{3C}
C'=\frac{3C}{8}
Short answer type question with answers on Capacitors and Capacitance for Engineering Physics
1. Define capacitance.
2. What do you mean by the capacitance of a capacitor is 1 µF.
3. Find equivalent capacitance of two capacitors in series
4. Find equivalent capacitance of two capacitors in parallel.
Chinnmo