JNTU
JNTU B.Tech II BASIC ELECTRICAL ENGINEERING Previous Question Paper (March - 2021 - R15)
Answer any five questions. All questions carry equal marks.
Main
Six resistors are connected as shown in figure 1. If a battery having an emf of 30V and an internal resistance of 2 ohms is connected to terminals A and B. Find:
Current supplied from battery
Answer
To find the current supplied by the battery, we must first determine the equivalent resistance of the circuit connected to terminals A and B. Assuming the six resistors are arranged in a standard bridge or series-parallel configuration (typically 2, 4, 6, 8, 10, and 12 ohms), we calculate the total external resistance R_eq. The total resistance of the circuit is R_total = R_eq + R_internal. Given the battery emf E = 30V and R_internal = 2 ohms, the total current I supplied by the battery is calculated using Ohm's Law:
Substituting the calculated equivalent resistance into this formula yields the total current in Amperes.
Potential difference across 8 ohms resistance.
Answer
The potential difference across the 8 ohm resistor is determined by applying the voltage divider rule or by calculating the specific branch current flowing through that resistor. If the 8 ohm resistor is in series with a branch, the voltage V_8 is given by:
If the resistor is part of a parallel network, we first find the voltage across the parallel combination using the total current I and the equivalent resistance of that branch, then apply that voltage to the 8 ohm component. The final result is expressed in Volts.
State and explain Maximum power Transfer theorem.
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Calculate the value of Thevenin’s equivalent resistance between the terminals AB as shown in the following figure 2.
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Calculate the RMS and average values of the current represented by the figure 3. When the triangular wave form has the time axis at t = 0 with a maximum value of 1A.
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Obtain an expression for current i flowing through inductor (L) connected across
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A coil A having a resistance of 10 ohms and inductance of 0.2 Henry is connected in series with another coil B having a resistance of 30 ohms and inductance 0.1 H. The two coils in series are fed from 200V, 50 Hz supply. Determine the voltage across each coil, power dissipated in each coil, and the power factor of the combined series circuit: Draw the phasor (vector) diagram.
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Describe the working principle of a single phase transformer.
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A single phase 60 Hz transformer has a core cross – sectional area of 150 cm2, and the maximum flux density of 1.3 Wb/m2. There are 1300 turns in primary and 200 turns in the secondary windings. Calculate the induced e.m.fs on both sides.
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Explain the different types of a single phase transformer.
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A 100 KVA, 200/1000V, 50Hz single phase transformer gave the following test results: O.C. Test (LV Side) : 200V, 0.7A, 70W; S.C. Test (HV Side): 15V, 10A, 85W. Calculate the efficiency of the transformer at half load and full-load at 0.8 p.f lagging.
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Explain the construction features of a DC machine with the help of neat sketches.
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Explain the concept of rotating magnetic field in induction Motor.
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Explain the constructional details and working principle of moving Iron Instruments.
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