1(a)
Find equivalent resistance across the terminal AB.

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!mage

3 M

1(b)
Find load resistance which dissipate maximum power.

3 M

1(c)
Find the rms value of a sinusoidal waveform.

3 M

1(d)
Draw resonance graph and write any four conditions of series reasonance.

3 M

1(e)
Write equations for three phase active power ans reactive power along with its units.

2 M

1(f)
Derive the conditions for maximum efficiency of a single phase transformer.

4 M

1(g)
Draw the input and output voltage waveform of a half wave rectifier.

2 M

2(a)
Using Mesh analysis find current through 2Ω resistor.

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!mage

6 M

2(b)
The impedances (12) Ω and (10-j20) Ω are connected in parallel and current through 12Ωis 10<0. Determine current through other branch, total current and kVA, kVAR, kW and power factor of the whole circuit.

8 M

2(c)
Draw phasor diagram of a single phase transformer connected to a inductive load.

6 M

3(a)
In a delta connected load each phase consists of a resistance of 100Ω in series with a capacitor of capacitance 31.8μF. When it is connected to a 400 V, three phase 50Hz supply calculate < br> i) the line current ii) Power factor iii) The power absorbed and iv) total kVA.

8 M

3(b)
A 50 kVA, 2200/220V, 50 Hz single phase transformer gave the following test results. Open circuit test(H.V side): 2200 V, 0.5A, 1000W

Short circuit test (H.V side): 100V, 20 A, 500 W

Determine i) Half load efficiency at 0.8 pf lagging and

ii) KV A at which maximum efficiency occurs and maximum efficieny at unity power factor

Short circuit test (H.V side): 100V, 20 A, 500 W

Determine i) Half load efficiency at 0.8 pf lagging and

ii) KV A at which maximum efficiency occurs and maximum efficieny at unity power factor

6 M

3(c)
With neat circuit diagram and characteristics explain the input and output characteristics of a CE transistor configuration.

4 M

3(d)
Draw the circuit diagram and output voltage waveform of a full wave bridge rectifier with capacitor filter.

2 M

4(a)
Find current through 10Ω using source transformation.

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!mage

7 M

4(b)
A balanced three phase star connected load has an impedance of 50<60Ω each phase connected across a three phase 1100 V, 50Hz supply. Two watt meters are used to measure power. Find the reading of each wattmeter.

4 M

4(c)
An alternating current of frequency 50 Hz has a maximum value of 12 A. Write down instantaneous current eauation. Find the value of current after 2.77 ms. Also find time taken to reach 9.6 A for the first time.

5 M

4(d)
Derive rectification efficiency and ripple factor of a full wave centre tapped rectifier.

4 M

5(a)
Calculate the current through 5Ω resistor using Thevenin's theorem.

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!mage.

8 M

5(b)
For an RL circuit prove that average power over one complete cycle is V

_{rms}I_{rms}cosθ.
4 M

5(c)
A 12 kVA, 400/200 V single phase 50Hz transformer has maximum efficiency of 95% at 85% of full load at unity power factor. Determine the efficiency at full load at 0.8 power factor lagging.

8 M

6(a)
Find current through 9Ω resistor using superposition theorem.

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!mage

7 M

6(b)
A series RLC circuit has the following parameter values R=10Ω, L=0.01H, C=100μH. Compute the resonant frequency , Q factor of the circuit , band width, lower and upper cut off frequency.

7 M

6(c)
Prove that the power and power factor in a balanced three phase circuit can be calculated form the reading of two watt meters. Draw relevant connection and phasor diagram.

6 M

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