Multiple choice Questions (MCQS)

Question 1:

Twelve 6Ω resistors are used as edge to form a cube. The resistance between two diagonally opposite corner of the cube is ---------------


a) 5/6 Ω           b) 6/5 Ω             c) 5Ω                d) 6Ω

Solution:

Current i will be split into 3 branch currents.

Since the resistance is same (i.e. 6 Ω), Current in each branch will be i/3.

This i/3 current will in turn split into 2 branch currents each of value i/6.

The current between 2 diagonally opposite side will be composed of two i/3 currents and one i/6 current.

(i/3) + (i/3) + (i/6) = 5i/6 ==>(V/R)

V = 5i; Req= V/i = 5i/i = 5Ω

Ans: c

Question 2:

The below graph shows the plot of current i(t) through a series R-L circuit when a constant forcing function of magnitude Vs =50 V is applied to it. Calculate the values of resistance R and L.

Solution:

The steady state current flowing through the circuit = 10 A. The time taken to reach 63.2 % of 10 A (i.e. 6.32 A) is 0.3. (i.e τ = 0.3 secs) .

I) i(steady state) = Vs / R

10 = 50/R

R = 5Ω

II) τ = L/R

0.3 = L/5

L = 0.3 * 5 = 1.5 H

Question 3:


The equivalent capacitance of the below circuit is

a) 3.5µF b) 1.2µF c) 2.4 µF d) 2.6 µF

Solution:

{(2 µF ǁ 1 µF) + 1.5 µF} ǁ 2.5 µF

{3 µF + 1.5 µF} ǁ 2.5 µF

{ 1 µF} ǁ 2.5 µF = 3.5 µF

Question 4:

In the below lattice network the value of RL for maximum power transfer is:

a) 6.67Ω              b) 9 Ω                    c) 6.52 Ω                 d) 8 Ω

Solution:

Looking into the circuit from R_L side :

R_TH = (7 ǁ 6) series (9 ǁ 5) = 6.5 Ω

For Maximum Power Transfer, R_L = R_TH.
Therefore RL = RTH = 6.52 Ω

Ans : C

Question 5:
In silicon at T=300K, the thermal equilibrium concentration of electron is n_o = 5 x 10⁴ cm^-3. The hole concentration is
 
a) 4.5 x 10¹⁵ cm^-3         b)  4.5 x 10¹⁵ m^-3

c) 0.3 x 10-6 cm-3               d) 0.3 x 10-6 m^-3

Solution:
n_op_o = n_i²

Given that n_o = 5 x 10⁴ cm^-3.

n_i for Si at room temperature is 1.5 x 10¹⁰

p_o =  n_i² /n_o

p_o = ( 1.5 x 10¹⁰)²    ⁄ 5 x 10⁴
p_o = 4.5 x 10¹⁵ cm^-3

Ans: a) 4.5 x 10¹⁵ cm^-3

Question 6:

A schottky diode clamp is used along with a switching BJT for

a) Reducing the power dissipation

b) Reducing the switching time

c) Increasing the value of β

d) Reducing the base current

Correct option is b) Reducing the switching time.

Question 7:

In an integrated circuit, the SiO₂ layer provides

a) Electrical connection to external circuit

b) Physical strength

c) Isolation

d) Conducting path

Correct option is c) Isolation

Question 8:

The flag which is not used for branching in a microprocessor is

a) Carry flag

b) Auxiliary flag

c) Overflow flag

d) Parity flag

Correct option is b) Auxiliary flag

Question 9:

In a 4-bit weighted-resistor D/A converter, the resistor value corresponding to LSB is 32kΩ. The resistor value corresponding to the MSB will be

a) 32kΩ

b) 16kΩ

c) 8kΩ

d) 4kΩ

Solution:

R = 32K / (2)3

R = 32K / 8

R= 4KΩ

Correct option is d) 4KΩ

Question 10:

A high Q coil has

a) Large bandwidth

b) High losses

c) Low losses

d) Flat response

Correct option is c) Low losses

Question 12:


A zener diode works on the principle of

a) Tunnelling of charge carriers across the junction

b) Thermionic emission

c) Diffusion of charge carriers across the junction

d) Hopping of charge carriers across the junction

Correct option is c) Diffusion of charge carriers across the junction

Question 13:

Kirchoff’s laws are not applicable to circuits with

a) Distributed parameters

b) Lumped parameters

c) Passive elements

d) Non-linear resistances.

Correct option is a) Distributed parameters.

Question 14 :
Skin effect occurs when a conductor carries current at

a) Very low frequencies

b) Low frequencies

c) High frequencies

d) None of these

Correct option is c) High frequencies.