Basic Electrical Engineering Questions and Answers
Calculate the total resistance between the points A and B.
a) 7 ohm
b) 0 ohm
c) 7.67 ohm
d) 0.48 ohm
Ans. C
1 ohm in parallel with 2 ohm give 2/3 ohm equivalent which is in series with 4 ohm and 3 ohm so total resistance between A and B = 4 + 2/3 + 3 = 23/3 = 7.67 ohm.
Q2.
Calculate the equivalent resistance between A and B.
a) 60 ohm
b) 15 ohm
c) 12 ohm
d) 48 ohm
Ans: c
5 ohm and 15 ohm are connected in series to give 20 ohm.10ohm and 20 ohm are connected in series to give 30 ohm. Now both equivalent resistances (20ohm and 30 ohm) are in parallel to give equivalent resistance 20*30/(20+30) = 12 ohm.
Q3.
Calculate the resistance between A and B.
a) 3.56 ohm
b) 7 ohm
c) 14.26 ohm
d) 29.69 ohm
Ans: a
The 1 ohm, 2 ohm and 3 ohm resistors are connected in parallel. Its equivalent resistance is in series with the 4 ohm resistor and the parallel connection of the 5 ohm and 6 ohm resistor. The equivalent resistance of this combination is 80/11 ohm. This is in parallel with 7 ohm to give equivalent resistance between A and B is 3.56 ohm.
Q4.
Calculate the equivalent resistance between A and B.
a) 2 ohm
b) 4 ohm
c) 6 ohm
d) 8 ohm
Ans: b
R=((2+3)||5)+1.5)||4. The 2 and the 3 ohm resistor are in series. The equivalent of these two resistors is in parallel with the 5 ohm resistor. The equivalent of these three resistances is in series with the 1.5 ohm resistor. Finally, the equivalent of these resistances is in parallel with the 4 ohm resistor.
Q5.
Calculate the equivalent resistance between A and B.
a) 6.67 ohm
b) 46.67 ohm
c) 26.67 ohm
d) 10.67 ohm
Ans: a
R=20||20||20=6.67 ohm. The three 20 ohm resistors are in parallel and re-sistance is measured across this terminal.
Q6.
Find the value of v if v1=20V and value of current source is 6A.
a) 10V
b) 12V
c) 14V
d) 16V
Ans: b
The current through the 10 ohm resistor=v1/10=2A.Applying KCL at node 1: i5=i10+i2. i2=6-2=4A.
Thus the drop in the 2 ohm resistor = 4×2 = 8V.
v1=20V; hence v2=20-v across 2 ohm resistor=20-8=12V
v2=v since they are connected in parallel.
v=12V.
Q7.
Calculate the current A.
a) 5A
b) 10A
c) 15A
d) 20A
Ans: c
KCl states that the total current leaving the junction is equal to the current entering it. In this case, the current entering the junction is 5A+10A=15A.
Q8.
Calculate the current across the 20 ohm resistor.
a) 20A
b) 1A
c) 0.67A
d) 0.33A
Ans: d
Assume lower terminal of 20 ohm at 0V and upper terminal at V volt and applying KCL, we get V/10 +V/20 =1. V=20/3V So current through 20 ohm = V/20 = (20/3)/20 =1/3=0.33V.
Q9.
Calculate the value of I3, if I1= 2A and I2=3A.
a) -5A
b) 5A
c) 1A
d) -1A
Ans: a
According to KCl, I1+I2+I3=0. Hence I3=-(I1+I2)=-5A.
Q10.
Find the value of i2, i4 and i5 if i1=3A, i3=1A and i6=1A.
a) 2,-1,2
b) 4,-2,4
c) 2,1,2
d) 4,2,4
Ans: a
At junction a: i1-i3-i2=0. i2=2A.
At junction b: i4+i2-i6=0. i4=-1A.
At junction c: i3-i5-i4=0. i5=2A.
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