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Electronic Devices & Circuits Mcqs

Q:

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
 
Answer & Explanation Answer: D) 1.67 mF

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.

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53
Q:

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
 
Answer & Explanation Answer: C) 5

Explanation: Not available for this question

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44
Q:

The energy required to move 120 coulomb through 3 V is _________

A) 25 mJ B) 360 J
C) 40 J D) 2.78 mJ
 
Answer & Explanation Answer: B) 360 J

Explanation: W = Qv = 360 J.

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59
Q:

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
 
Answer & Explanation Answer: B) 2 A

Explanation: i = dQ/dt = 120/60 = 2A.

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59
Q:

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
 
Answer & Explanation Answer: D) 1.5 C

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

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107
Q:

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
 
Answer & Explanation Answer: C) 16.02 C

Explanation: n 10²?, Q = ne = e 10²? = 16.02 C.
Charge on sphere will be positive.

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