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BEE

Unit – 1DC Circuits Q1) Find maximum power delivered is RLif its value is

16Ω
Ω
60Ω
20Ω

A1)

Therefore,

Q2) Find out the value of load resistance if power absorbed is maximum.

A2)

Find Thevenin’s equation

Q3) Find out the Norton’s equivalent

A3)

Since, there is no significance of current source

Q4) Find Vth

A4)

For Rth

By KCL,

But,

By KVL,

Q5) Find I.

A5)

1 =

2 =

1 + 2

Q6) Find the current through

resistance using superposition theorem.

A6)

1= 0

1 + 2

Q7) Convert Star to delta to find equivalent resistance.

$C:\Users\ManishM\Downloads\BEE5_1$

A7)

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 +

Q8) Why ideal Current source has infinite resistance?A8) A current source is used to power a load, so that load will turn on. We try to supply 100% of the power to load. For that, we connect some resistance to transfer 100% of power to load because the current always takes the path of least resistance. So, in order for current to go to the path of least resistance, we must connect resistance higher than load. This is why we have the ideal current source to have infinite internal resistance. This infinite resistance will not affect voltage sources in the circuit. Q9) State and explain Maximum Power Transfer Theorem.A9)

Where Rth is Thevenin’s equivalent resistance across a and b.

Maximum power is absorbed by ZL when

Condition:

Comparing real and imaginary parts

Maximum power absorbed by ZL is

Q10) Write a note on ideal and practical voltage source.A10)

Ideal Voltage Source

img 2.png

Fig: Ideal Voltage Source

The graph represents the change in voltage of the voltage source with respect to time. It is constant at any instance of time.

Voltage sources that have some amount of internal resistance are known as a practical voltage source. Due to this internal resistance, voltage drop takes place. If the internal resistance is high, less voltage will be provided to load and if the internal resistance is less, the voltage source will be closer to an ideal voltage source. A practical voltage source is thus denoted by a resistance in series which represents the internal resistance of source.

Practical Voltage source

img 2.png

Fig: Practical Voltage source

The graph represents the voltage of the voltage source with respect to time. It is not constant but it keeps on decreasing as the time passes.

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