Two Mark Questions and Answers

TWO MARK QUESTIONS AND ANSWERS

1. State Superposition theorem. (AU/EEE NOV 2007, MAY 2008)

"In a linear network containing several sources (including dependent sources), the over all response (branch current or voltage) in any branch in the network equals the algebraic sum of the responses of each individual source considered separately with all other sources made inoperative. i.e replaced by their internal resistances or impedances".

2. State Thevenin's theorem. (AU/EEE- MAY 2007, MAY 2008)

Across a pair of terminals AB, any linear network can be replaced by an equivalent circuit composed of a voltage source V_OC  in series with resistance R_th. The voltage Voc is the voltage across the open circuited terminals AB and Rth is the equivalent resistance of the network as seen from terminals AB with all independent sources are replaced by their internal resistances.

where,

V_OC  → Open circuit voltage across terminals AB

R_th → Thevenin's resistance

3. State Norton's theorem. (AU/EEE- MAY 2005)

Any two terminal network containing linear, passive and active elements may be replaced by an equivalent current source I_N in parallel with a resistance R_th where

I_N is the current flowing through a short circuit placed across the terminals AB and R_Th is the equivalent resistance of the network as seen from the two terminals with all independent sources are replaced by their internal resistances.

where

I_N → Short circuit current through AB

R_Th →Thevenin's Resistance

4. State maximum power transfer theorem. (AU/EEE- MAY 2008)

In DC circuits, maximum power is transferred from a source to the load when the load resistance is made equal to the resistance of the network as viewed from the load terminals with load removed and all the sources are replaced by their internal resistances.

5. State reciprocity theorem. (AU/EEE- NOV 2007)

In any linear network containing bilateral linear resistances and energy sources, the ratio of a voltage V introduced in one mesh to the current I in any second mesh is the same as the ratio obtained if the positions of V and I are interchanged, other voltages sources are being removed.

6. What is the condition for maximum power transfer? (AU/EEE- NOV 2008)

The power delivered is maximum if the load resistance is equal to the source resistance.

7. Write some applications of maximum power transfer theorem.

1. Power amplifiers.

2. Communication systems.

3. Microwave transmission.

8. What is the limitation of Superposition theorem?

This theorem is valid only for linear systems. This theorem can be applied for calculating the current through or voltage across any particular element. But, this Superposition theorem is not applicable for calculation of power.

9. Under what conditions Superposition theorem may be applied?

Superposition theorem can be applied only when the cause and effect have a linear and relationship.

10. What are the limitations of Maximum power transfer theorem?

The maximum efficiency which can be obtained by using this theorem is only 50%. It is because 50% of the power is unnecessarily wasted in R_th

Therefore, this theorem is applicable only for communication circuits and not for power circuits where efficiency is of given more importance rather than power delivered.