JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech II ELECTRICAL SYSTEMS Previous Question Paper (August/September - 2022 - R13)
Answer any five questions. All questions carry equal marks.
Main
State and explain Norton’s theorem.
Answer
Norton's theorem states that any linear, bilateral, active two-terminal network containing sources and impedances can be replaced by an equivalent circuit consisting of a current source in parallel with an impedance. The current source, known as the Norton current (I_N), is equal to the short-circuit current flowing between the two terminals, and the impedance, known as the Norton impedance (Z_N), is the equivalent impedance of the network as viewed from the terminals with all independent sources replaced by their internal impedances.
The procedure involves: 1) Short-circuiting the load terminals to calculate the short-circuit current I_N. 2) Removing all independent sources (short-circuiting voltage sources and open-circuiting current sources) to calculate the equivalent impedance Z_N looking into the terminals. 3) Drawing the equivalent circuit with I_N in parallel with Z_N and the load connected across the terminals.
Find the current flowing through 3 Ω resistance using Thevenin’s theorem (figure 1).
Answer
To find the current through the 3 Ω resistor using Thevenin's theorem, follow these steps:
- Remove the 3 Ω load resistance to create an open circuit at the terminals A and B.
- Calculate the Thevenin voltage (V_th) across terminals A and B. This is the open-circuit voltage determined by applying nodal or mesh analysis to the remaining circuit.
- Calculate the Thevenin resistance (R_th) by deactivating all independent sources (shorting voltage sources and opening current sources) and finding the equivalent resistance seen from terminals A and B.
- Connect the 3 Ω resistor back in series with V_th and R_th to form the Thevenin equivalent circuit.
- Calculate the load current (I_L) using the formula:
where R_L = 3 Ω. The resulting value gives the current flowing through the specified branch.
State and explain Reciprocity theorem.
Answer
Sign in to view the complete answer paper.
Find the current flowing through 10 ohms using superposition theorem (figure 2).
Answer
Sign in to view the complete answer paper.
Obtain the relation between line quantities and phase quantities in Star connection.
Answer
Sign in to view the complete answer paper.
An inductance of 0.5 H, a resistance of 5 ohm and a capacitance of 8 μF are in series across a 220 V a.c supply. Calculate the frequency at which the circuit resonates.
Answer
Sign in to view the complete answer paper.
A series combination of R = 2 Ω; L = 1 H is connected across a step voltage of 20 volts through a switch. Find the current flowing through the circuit when the switch is closed at t = 0. Use Laplace transform.
Answer
Sign in to view the complete answer paper.
An alternating voltage (50+ j80) volt is applied to a circuit and current flowing is (4-j10) amps. Find the (i) impedance of the circuit and (ii) power factor (iii) active and reactive power.
Answer
Sign in to view the complete answer paper.
Draw the phasor diagram of 1-phase transformer on no-load.
Answer
Sign in to view the complete answer paper.
Explain the principle of operation of a single phase transformer.
Answer
Sign in to view the complete answer paper.
The following test results were obtained in a 250/500 V transformer: O.C. test: 250 V, 2A, 70W; S.C. test: 20V, 10A, 90W. Determine:
a) Efficiency when the output is 10 A at 500 V and 0.8 p.f lagging
b) The regulation at u.p.f
Answer
Sign in to view the complete answer paper.
State the principle of operation of D.C. Generator and derive the expression for the emf generated.
Answer
Sign in to view the complete answer paper.
What is armature reaction in d.c generators? Discuss in detail.
Answer
Sign in to view the complete answer paper.
What are the constructional features of both squirrel cage induction motor and slip ring induction motor?
Answer
Sign in to view the complete answer paper.
Explain the measurement of 3-phase power using two wattmeter method.
Answer
Sign in to view the complete answer paper.