UNIT 1

D.C. Circuits

Q1) Find the current through resistance. Using superposition theorem?

Solution:

1= 0

2=

1 + 2 

Q2) Find Current I using superposition theorem?

Sol: 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).

1 =

2 =

=

1 + 2

  =

Q3) Find Vth and Rth?

Sol:

Finding Isc from circuit directly:

By KCL,

Q4) Find Rth and Vth?

Sol:

Also, clear from circuit that Vth = 1V.

By applying KVL we get,

1-3Isc=0

Isc=A

Q5) Find Rth and Isc?

Sol:

Rth=3k+2k=5k

By applying KVL we get

Therefore,

Q6) Find Vx?

Solution: For Rth

By KCL,

     But,

By KVL,

Q7) Find i?

Solution: Since, no independent source is present so,

Isc = 0

And we know that,

Since Rth cannot be zero

       But

Q8) Find out the Norton’s equivalent

Solution:

Since, there is no significance of current source

A

Q9) For the circuits given below write the voltage equations:

Solution: Let current i1be in loop 1 current and i2 for loop 2 

Q10) For the circuits given below write the voltage equations

Solution:

For loop 1 

For loop 2 

Q11) Using nodal analysis find voltage across 5resistor.

Solution:

For V1

1

For V2

2

Solving 1 and 2:

For 5 voltage =

= -50.9 + 57.27

= 6.37V

Q12) Find

Sol:

Q12) Find

Sol:

Q13) Use nodal analysis to find current in the circuit?

Sol: + +3i=4

+ -3i= -3

But i=

Substituting and solving above equation we get

V2 = 10V

i= = 2A

Q14) Find equivalent resistance R?

Sol: Equivalent resistance across ab = = 4Ω

Equivalent resistance across cd = =1 Ω

Req = Rab||Rcd +3 = + 3 = 19/5 Ω