Basic Electrical Engineering Questions and Answers
Q1.
If a 1ohm 2ohm and 32/3ohm resistor is connected in star, find the equivalent delta connection.
a) 34 ohm, 18.67 ohm, 3.19 ohm
b) 33 ohm, 18.67 ohm, 3.19 ohm
c) 33 ohm, 19.67 ohm, 3.19 ohm
d) 34 ohm, 19.67 ohm, 3.19 ohm
Ans: a
Using the formula for delta to star conversion:
Using the formula for delta to star conversion:
R1=1+2+1*2/(32/3)
R2=1+32/3+1*(32/3)/2
R3=2+32/3+2*(32/3)/1.
Q2.
If an 8/9ohm, 4/3ohm and 2/3ohm resistor is connected in star, find its delta equivalent.
a) 4ohm, 3ohm, 2ohm
b) 1ohm, 3ohm, 2ohm
c) 4ohm, 1ohm, 2ohm
d) 4ohm, 3ohm, 1ohm
Ans: a
Using the formula for the star to delta conversion:
R1=8/9+4/3+(8/9)*(4/3)/(2/3)
R2=8/9+2/3+(8/9)*(2/3)/(4/3)
R3=2/3+4/3+(2/3)*(4/3)/(8/9).
Q3.
The maximum power drawn from source depends on __________
a) Value of source resistance
b) Value of load resistance
c) Both source and load resistance
d) Neither source or load resistance
Answer: b
Q4.
The maximum power is delivered to a circuit when source resistance is __________ load resistance.
a) Greater than
b) Equal to
c) Less than
d) Greater than or equal to
Answer: b
Q5.
If source impedance is a complex number Z, then load impedance is equal to _________
a) Z’
b) -Z
c) -Z’
d) Z
Answer: a
Q6.
If ZL=Zs’, then RL=?
a) -RL
b) Rs
c) -Rs
d) 0
Answer: b
Q7.
Does maximum power transfer imply maximum efficiency?
a) Yes
b) No
c) Sometimes
d) Cannot be determined
Answer: b
Q8.
Under the condition of maximum power efficiency is?
a) 100%
b) 0%
c) 30%
d) 50%
Answer: d
Efficiency=(Power output/ Power input)*100.
Power Output=I2RL, Power Input=I2(RL+RS)
Under maximum power transfer conditions, RL=RS
Power Output=I2RL; Power Input=2*I2RL
Thus efficiency=50%.
Q9.
Name some devices where maximum power has to be transferred to the load rather than maximum efficiency.
a) Amplifiers
b) Communication circuits
c) Both amplifiers and communication circuits
d) Neither amplifiers nor communication circuits
View Answer
Answer: c
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