Solve any one question from Q1 and Q2

1 (a)
Obtain the equation for coefficient of coupling between two coils placed on common magnetic field.

6 M

1 (b)
A water pump lifts 50 m

^{3}of water per hour to a height of 20 m. The overall efficiency of water pump set is 0.60. Find monthly bill, when the pump is used 4 hours a day for a month of 30 days, at the rate of Rs. 5/kWh.
6 M

2 (a)
Explain the effect of temperature on resistance of:

(i) metal conductors

(ii) insulators

(iii) alloys.

(i) metal conductors

(ii) insulators

(iii) alloys.

6 M

2 (b)
A steel ring of mean diameter of 50 cm is wound with
500 turns on it. A flux density of 1 Tesla is produced in
the ring by mmf of 4000 AT/m. Calculate magnetising current. Also find the current when an air gap of 1 mm is cut in it, keeping B = 1 Tesla in the ring.

6 M

Solve any one question from Q3 and Q4

3 (a)
Obtain the expression for composite capacitor having 3-dielectric materials.

7 M

3 (b)
A 50 Hz sinusoidal voltage has rms value of 200 V. At
t = 0, the instantaneous value is positive and half of its maximum value. Write down the expression for voltage and sketch the wave form.

6 M

4 (a)
Derive an equation for average value of sinusoidal current in terms of its peak value.

6 M

4 (b)
A 40 kVA, 2200/220 V, 50 Hz, 1-ph transformer has an iron loss of 250 W. The resistances of low and high voltage windings are 0.005 Ω and 0.5 Ω respectively. Calculate efficiency at full load and load p.f. = 0.8 lagging.

7 M

Solve any one question from Q5 and Q6

5 (a)
Obtain the expression for power, if x = v

_{m}sin out is applied to R-L series circuit.
6 M

5 (b)
Three identical impedances each of 6 + j8 Ω are connected
in star across 3-ph, 400 V, 50 Hz a.c. supply. Calculate:

(i) line current

(ii) active power

(iii) reactive power.

(i) line current

(ii) active power

(iii) reactive power.

7 M

6 (a)
What is series resonance? Obtain the equation for resonant frequency.

6 M

6 (b)
Two circuits having impedances Z

(i) current drawn by each circuit

(ii) total current

(iii) p.f. of whole circuit.

_{1}= 8 + j6 Ω and Z_{2}= 5 +j10 Ω are connected in parallel across 200 V, 50 Hz, 1-ph a.c. supply. Calculate:(i) current drawn by each circuit

(ii) total current

(iii) p.f. of whole circuit.

7 M

Solve any one question from Q7 and Q8

7 (a)
Using simple series-parallel combination, find R

_{BC}for Fig 1.

6 M

7 (b)
Obtain the equations to convert A-connected resistances into equivalent star circuit.

6 M

8 (a)
State the Thevenin's theorem and explain the steps to find R

_{th}, V_{th}and I_{th}.
6 M

8 (b)
Using Mesh/Loop analysis, calculate current flowing through R

_{BC}for Fig 2.

6 M

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