Quiz: Electrical Engineering 07 Apr 2021

Quiz: Electrical Engineering
Topic: Miscellaneous

Each question carries 1 mark.
Negative marking: 1/3 mark
Time: 10 Minute

Q1. Two resistors A and B have resistance R_A and R_B respectively with R_Aρ_B
(b) ρ_A=ρ_B
(c) ρ_A<ρ_B
(d) Information insufficient

Q2. The power dissipated in a resistor in terms of its conductance G and the voltage V across it is
(a) V²G
(b) V²/G
(c) G²V
(d) G²/V

Q3. The total charge entering the terminal of an element is given by;
q = (6t² – 12t) mC
The current at t = 3s is
(a) 12 mA
(b) 48 mA
(c) 36 mA
(d) 24 mA

Q4. Three conductance G₁ = 0.5 S, G₂ = 0.3 S and G₃ = 0.2 S are in parallel. If the total circuit current is 4 A, current in G₁ is
(a) 1.2 A
(b) 2 A
(c) 0.8 A
(d) None of the above

Q5. A Wheatstone bridge in balanced. If the galvanometer is short-circuited, the currents in the various resistors will
(a) increase
(b) decrease
(c) not change
(d) cannot say

Q6. Two cells of the same e.m.f. E but of different internal resistances r₁ and r₃ are connected in series with an external resistance R. The potential drop across the first cell is found to be zero. The external resistance R is
(a) r₁ + r₂
(b) r₁ – r₂
(c) r₂ – r₁
(d) r₁×r₂

Q7. A linear circuit is one whose parameters (e.g., resistances etc.) …………………………….
(a) change with change in current
(b) change with change in voltage
(c) do not change with voltage and current
(d) None of the above

Q8. What is the average value of sinusoidal wave form over one completer cycle?
(a) zero
(b) V_m \/π
(c) (2V_m)/π
(d) 2π/V_m

Q9. A load is connected to a circuit. At the terminals to which the load is connected, R_Th = 10 Ω and V_Th = 40 V. The maximum power supplied to the load is
(a) 160 W
(b) 80 W
(c) 1 W
(d) 40 W

Q10. When a network is loaded by a resistance equal in value to its Norton resistance, the Norton current is I_N. The current through the load will be
(a) I_N/4
(b) 2I_N
(c) I_N/2
(d) None of these


S1. Ans.(d)
Sol. Resistance (R)=ρL/A
From this relation we can understand that the resistance also depends on length and area of the conductor. because in question it is not given that area and length are constant or any dependence of them over resistance.
So, we cannot deduce the values of resistivity directly from the values of the resistance. Hence correct option is D.

S2. Ans.(a)
Sol. Power dissipated,
P=V^2/R=V^2×1/R=V^2 G

S3. Ans.(d)
Sol. Current, i=dq/dt=d/dt (q)=d/dt (6t^2-12t)=(12t-12) mA
At t = 3s, i = 12 × 3 – 12 = 36 – 12 = 24 mA

S4. Ans.(b)
Sol. Total conductance, G_T = G₁ + G₂ + G₃ = 0.5 + 0.3 + 0.2 = 1 S
∴ Current in G₁ = 4×G_1/G_T =4×0.5/1=2 A

S5. Ans.(c)
Sol. Since the bridge is balanced, there is no current in the branch containing galvanometer.
Therefore, whether the branch containing galvanometer is shorted or open-circuited, there will be no change in currents or voltages anywhere in the circuit.

S6. Ans.(b)
Sol. Circuit current, I=2E/(R + r_1 + r_2 ); Drop across first cell = E – Ir₁
It is given that: E – Ir₁ = 0
or,E-(2Er_1)/(R+r_1+r_2 )=0
∴ R = r₁ – r₂

S7. Ans.(c)
Sol. A linear circuit is an electric circuit in which circuit parameters (Resistance, inductance, capacitance, waveform, frequency etc.) are constant. In other words, a circuit whose parameters are not changed with respect to Current and Voltage is called Linear Circuit.

S8. Ans.(c)
Sol. V_avg=(2V_m)/π

S9. Ans.(d)
Sol. Under maximum power transfer, R_L=R_Th and voltage across R_L=V_Th/2.
∴P_(max.)=(V_Th/2)²/R_Th =(40/2)²/10=40 W

S10. Ans.(c)
Sol. Under maximum power transfer, R_L=R_N. Therefore, the Norton current will divide equally between R_L and R_N so that current through R_L is I_N/2.


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