1.a. Describe with necessary graph the effect of temperature on resistance of following material:

a) metals

b) insulation.

1.b. An air cored loroid having 25 cm mean diameter and 6.26 cm² circular across sectional area would uniformly with 1000 turns of wire. Determine

i) inductance of loroid.

ii) emf induced in the coil when current is increasing at the rate of 200A/sec.

iii) energy stored in its magnetic field when coil carries current of 10A.

2.a. In a hydro electric generating station the head of water is 425 cm. If 1250 litres of water are required to generate 1kWh of electric energy , find the overall efficiency. Assume 1 litre = 1kg.

2.b. Derive the formula of total reluctance and total mmf in following circuit if relative permeability are $\mu$₁ and $\mu$₂ respectively.

3.a. Give the types if capacitor based on dielectric material used and describe any two types.

3.b. A sinusoidal varying alternating current has r.m.s. value of 40 A and periodie time of 20 milliseconds. If the waveform of this current enters in to positive half cycle at t=0, find instantaneous values 3 of the current at quarter cycle, tl=7 ms and t2=14ms.

4.a. A50 KVA single phase transformer has a turn ratio of 300/20. The primary winding is connected to a 2200V , 50Hz supply. Calculate.

i) The secondary voltage at no load.

ii) The approximate value of a primary current on full load.

iii) The approximate value of secondary current on full load.

4.b. Explain the concept of lagging , leading and in phase phasors. Draw the respective waveform and phasor diagram for the same.

5.a. Derive the expression for current drawn and power consumed by a circuit consisting of a resistor R and a capacitor C connected in series across v = Vₙ sin ($\omega$t)

5.b. Each phase of star connected load has an impedance (25+j40) connected across 3-phase , 415 V , 50Hz supply. Determine:

a) Line current.

b) Active , Reactive and apparent power.

6.a. Derive the relationship between the line and phase value of voltage and current for balanced three phase star connective resistive load with the help of connection diagram and phasor diagram. Hence obtain the total power consumed.

6.b. Two impedance Z=30$\angle$40° $\Omega$ and Z = 45$\angle$30° $\Omega$ are connected in parallel across a single phases 230V , 50 Hz supply. Calculate the

i) current drawn,

ii) Power factor and

iii) power consumed by the circuit.

7.a. With usual notation, derive step by step formula for converting star elements of the network to delta elements on equivalent basis.

7.b. Calculate the current through all resistance using superposition principle.

8.a. Elaborate steps to be followed to obtain current through any branch using superposition theorem.

8.b. Determine effective resistance between A ans B.