JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech II Year BASIC ELECTRICAL AND ELECTRONICS ENGINEERING Previous Question Paper (August/September - 2022 - R18)
Answer any five questions. All questions carry equal marks.
Main
Calculate the current flowing through 8Ω resistor for the following circuit using Kirchoff’s Law shown in figure below.
Answer
To calculate the current through the 8Ω resistor using Kirchhoff's Laws, we apply Kirchhoff's Voltage Law (KVL) to the independent loops of the circuit. Assuming the circuit consists of two loops with mesh currents I1 and I2, we write the following equations:
For Loop 1:
For Loop 2:
Where R2 is the 8Ω resistor shared between the two loops. By substituting the known resistance and voltage values into these equations, we obtain a system of two linear equations with two variables. Solving this system yields the values for I1 and I2.
The current flowing through the 8Ω resistor is the net current resulting from the interaction of the two mesh currents, given by the absolute difference:
Once the values for I1 and I2 are determined via substitution or Cramer's rule, the magnitude and direction of the current through the 8Ω resistor are confirmed. If the calculated value is positive, the current flows in the assumed direction of the dominant mesh current; if negative, it flows in the opposite direction.
Explain frequency, time period, instantaneous value, maximum value and average value for a sinusoidal voltage.
Answer
Frequency (f) is the number of cycles completed by a sinusoidal waveform in one second, measured in Hertz (Hz). It is the reciprocal of the time period.
Time Period (T) is the time taken by the waveform to complete one full cycle, measured in seconds (s). Formula: T = 1 / f.
Instantaneous Value (v(t)) is the value of the voltage at any specific instant of time. It is represented as v(t) = Vm sin(ωt).
Maximum Value (Vm), also known as the peak amplitude, is the highest value attained by the waveform in either the positive or negative direction.
Average Value (Vavg) for a sinusoidal wave over a full cycle is zero. For a half-cycle, it is defined as the arithmetic mean of all instantaneous values, given by Vavg = 2Vm / π ≈ 0.637 Vm.
In an R–L–C series circuit, the voltage across R is 160 V, across L is 240 V, and power consumed is 1000 W when a voltage of 200 V at 50 Hz is applied across the circuit. Calculate the value of the capacitor and the current flowing through the circuit.
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Explain the following:
- Earth leakage Circuit breaker
- Switch fuse unit
- Moulded case Circuit breaker
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List the disadvantages of Low Power factor.
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List and explain the various types of Rechargeable and Non-Rechargeable batteries.
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A residential flat has the following average electrical consumptions per day:
- 4 tube lights of 40 watts working for 5 hours per day;
- 2 filament lamps of 60 watts working for 8 hours per day;
- 1 water heater rated 2 kW working for 1 hour per day;
- 1 water pump of 0.5 kW rating working for 3 hours per day.
Calculate the cost of energy per month if 1 unit of energy costs Rs.4.50.
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Draw the equivalent circuit of a transformer under the no-load condition and explain it.
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The wave-connected armature of a two-pole 200 V d.c. generator has 400 conductors and runs at 300 rpm. Calculate the useful flux per pole.
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What is the function of the following parts in a dc machine:
- Field poles
- Armature
- Brush
- Commutator
- Windings
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List and explain the various losses that occur in Induction Motors.
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List the Diode parameters and explain the significance of them in brief.
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Explain the functioning of the Zener Diode along with its symbol and V – I characteristics with a neat diagram and how it can be used as a voltage regulator.
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Explain the working of a p – n – p transistor with a neat diagram.
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Explain the construction of JFET.
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