Electronic Devices and Circuits Questions and Answers – Basic Concepts

This set of Electronic Devices and Circuits Multiple Choice Questions & Answers (MCQs) focuses on “Basic Concepts”.

1. A solid copper sphere, 10 cm in diameter is deprived of 1020 electrons by a charging scheme. The charge on the sphere is _________
a) 160.2 C
b) -160.2 C
c) 16.02 C
d) -16.02 C
View Answer

Answer: c
Explanation: n 1020, Q = ne = e 1020 = 16.02 C.
Charge on sphere will be positive.

2. A lightning bolt carrying 15,000 A lasts for 100 s. If the lightning strikes an airplane flying at 2 km, the charge deposited on the plane is _________
a) 13.33 C
b) 75 C
c) 1500 C
d) 1.5 C
View Answer

Answer: d
Explanation: dQ = i dt = 15000 x 100µ = 1.5 C.

3. If 120 C of charge passes through an electric conductor in 60 sec, the current in the conductor is _________
a) 0.5 A
b) 2 A
c) 3.33 mA
d) 0.3 mA
View Answer

Answer: b
Explanation: i = dQ/dt = 120/60 = 2A.
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4. The energy required to move 120 coulomb through 3 V is _________
a) 25 mJ
b) 360 J
c) 40 J
d) 2.78 mJ
View Answer

Answer: b
Explanation: W = Qv = 360 J.

5. Consider the circuit graph shown in figure below. Each branch of circuit graph represent a circuit element. The value of voltage V1 is:
The value of voltage V1 is 15 V if each branch of circuit graph represent circuit element
a) 30 V
b) 25 V
c) 20 V
d) 15 V
View Answer

Answer: d
Explanation: 100 = 65 + V2 => V2 = 35 V
V3 – 30 = V2 => V3 = 65 V
105 – V3 + V4 – 65 = 0 => V4 = 25 V
V4 + 15 – 55 + V1 = 0 => V1 = 15 V.
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6. What will be the value of Req in the following Circuit?
The value of Req in the following Circuit is 11.18 ohm
a) 11.86 ohm
b) 10 ohm
c) 25 ohm
d) 11.18 ohm
View Answer

Answer: d
Explanation: The same pattern followed after every 10ohm resistorWe infer from the given diagram that the same pattern is followed after every 10ohm resistor. The infinite pattern in parallel as a whole is considered as to be Rx.
Thus, Rx = R + (R||Rx)
Solving for Rx, we get Rx = 1.62R, where R=10ohm.
So we have Rx = (1.62ohm)*(10ohm), which gives Rx=16.2ohm
Therefore, Req = 5 + (10||16.2)
=> 5 + [(10*16.2)/(10+16.2)] => Req = 5 + (162/26.2) which gives Req=11.18 ohm.

7. In the circuit the dependent source __________
In the circuit the dependent source absorbs 32 W
a) supplies 16 W
b) absorbs 16 W
c) supplies 32 W
d) absorbs 32 W
View Answer

Answer: d
Explanation: P = VIx = 2Ix Ix = 2 x 16 or 32 watt (absorb).
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8. Twelve 6 ohm resistors are used to form an edge of a cube. The resistance between two diagonally opposite corner of the cube (in ohm) is ________
a) 5/6
b) 6/5
c) 5
d) 6
View Answer

Answer: c
Explanation: The resistance between two diagonally opposite corner of the cube is 5
The current I will be distributed to the cube branches symmetrically.
Connecting a voltage source Vab across the terminals and applying kvl in the outer loop, we have
=> -Vab + (i/3+i/6+i/3)*R = 0 (where R is given as 6ohm)
=> Vab = 5i
=> Req=Vab/i, which gives Req = 5ohm.

9. The energy required to charge a 10 µF capacitor to 100 V is ________
a) 0.1 J
b) 0.05 J
c) 5 x 10(-9) J
d) 10 x 10(-9) J
View Answer

Answer: b
Explanation: Energy provided is equal to 0.5 CVxV.
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10. A capacitor is charged by a constant current of 2 mA and results in a voltage increase of 12 V in a 10 sec interval. The value of capacitance is ________
a) 0.75 mF
b) 1.33 mF
c) 0.6 mF
d) 1.67 mF
View Answer

Answer: d
Explanation: The capacitor current is given as i=C*(dv/dt), where dv/dt is the derivative of voltage, dt=t2-t1 given as 10 sec and dv is the change in voltage which is given as 12V.
So, we have C=i/(dv/dt)
=> C = 2mA/(12/10) = 2mA/(1.2).
Hence C = 1.67mF.

Sanfoundry Global Education & Learning Series – Electronic Devices and Circuits.

To practice all areas of Electronic Devices and Circuits, here is complete set of 1000+ Multiple Choice Questions and Answers.

If you find a mistake in question / option / answer, kindly take a screenshot and email to [email protected]

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Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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