Unit 1
Unit 1
DC Circuits
Question 1. Find the current through 
resistance.
Solution:
1= 0
2=
1 + 
2 
Special Case:
Since two voltage sources with different magnitude in parallel which cannot be connected as in single branch two different current is not possible (if 5V than I = zero).
Question 2:
1 = 
2 = 
=
1 + 
2
= 
Question 3:
Answer:
Finding Isc from circuit directly:
By KCL,
Question 4:
Answer
Also, clear from circuit that Vth = 1V.
By applying KVL we get,
1-3Isc=0
Isc=
A
Que 5:
Ans;
Rth=3k+2k=5k
By applying KVL we get
Therefore, 
Question 6:
Solution: For Rth
By KCL,
But, 
By KVL,
Question 7:
Solution: Since, no independent source is present so,
Isc = 0
And we know that,
Since Rth cannot be zero
But 
Q 8 Explain Star Delta transformation
Star to delta conversion to final equivalent resistance
We know that (from delta to star conversion)
R1 = 
…….①
R2 = 
…..②
R1 = 
……③
Multiply ① X ② L.H.S and R.H.S
R1 R2 =
…….④ where 
Similarly multiply ② X ③
R2 R3 =
…….⑤
And ③ X①
R1 R3 =
…….⑥
Now add equation ④, ⑤, and ⑥ L.H.S and R.H.S
……refer eq. ②
= 
+ 
+ 
= 
+ 
(Delta)
star star
Similarly R23 = R2+R3 + 
R23 = R1+R2 + 
