Basic Electrical Engineering Questions and Answers
Q1.
Find the current in the circuit.
a) 1 A
b) 2 A
c) 3 A
d) 4 A
Ans. B
I=V/R. Total resistance R = 20+40=60ohm. V=120V. I=120/60=2A.
Q2.
Voltage across the 60ohm resistor is______
a) 72V
b) 0V
c) 48V
d) 120V
Ans. B
The 60ohm resistance is shorted since current always choses the low resistance path. Voltage across short circuit is equal to zero, hence voltage across the resistor is 0.
Q3.
Find the voltage across the 6 ohm resistor.
b) 181.6V
c) 27.27V
d) 54.48V
Ans. C
Total current I=150/(6+12+15)=(150/33)V.
V across 6 ohm = 6*I = 6*(150/33)V = 27.27V.
Q4.
What is the value of x if the current in the circuit is 5A?
a) 15 ohm
b) 25 ohm
c) 55 ohm
d) 75 ohm
Ans. A
Total voltage=sum of voltages across each resistor. =>150=10*5+5*5+5*x. Solving the equation, we get x=15 ohm.
Q5.
Calculate the current across the 20 ohm resistor.
a) 10A
b) 20A
c) 6.67A
d) 36.67A
Ans. A
I=V/R. Since in parallel circuit, voltage is same across all resistors. Hence across the 20 ohm resistor, V=200V so I=200/20=10A.
Q6.
Calculate the total current in the circuit.
a) 20 A
b) 10 A
c) 11.43 A
d) 15 A
Ans. C
The 1 ohm and 2 ohm resistor are in series which is in parallel to the 3 ohm resistor. The equivalent of these resistances (3/2 ohm) is in series with the 4 ohm and 5 ohm resistor. Total R = 21/2 ohm. I=V/R=120/(21/2)=240/21=11.43 A.
Q7.
The voltage across the open circuit is?
a) 100V
b) Infinity
c) 90V
d) 0V
Ans. A
The voltage across all branches in a parallel circuit is the same as that of the source voltage. Hence the voltage across the 10 ohm resistor and the open circuit is the same=100V.
Q8.
The voltage across the short is?
a) 135V
b) Infinity
c) Zero
d) 11.25V
Ans. C
The voltage across a short is always equal to zero whether it is connected in series or parallel.
Q9.
If the current through x ohm resistance in the circuit is 5A, find the value of x.
a) 27 ohm
b) 5 ohm
c) 12 ohm
d) 135 ohm
Ans. A
R=V/I. In this circuit I=5A and V=135V. Therefore, R=135/5=27 ohm.
Q10.
The total resistance between A and B are?
a) 20 ohm
b) 5 ohm
c) 80 ohm
d) 0 ohm
Ans. B
The resistors are connected in parallel, hence the equivalent resistance = 1/(1/20+1/20+1/20+1/20)=5A.
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