State whether the following statements are True or False:

1.(a)The resistance of a conductor increases, if its area of cross-section increases. Three resistances of R ohms each are connected in delta. Its equivalent star will comprise resistance of value R/3 each. The superposition theorem is applicable to only linear circuits. Magnetic flux density is the ratio of cross-sectional area to the magnetic flux The power factor of a purely resistive circuit is unity. In case of 3-phase delta connected circuit, the total power is given by sqrt(3) VL IL cos . The unit of electrical energy is

2.(a) Define power factor. Explain the concept of power triangle with the help of power factor.

(b) Calculate the value of form factor of a half wave rectified waveform.

3.(a) Derive an expression for the half cycle average value for sinusoidal current Im sin wt.
In the circuit shown, determine the current supplied by the 100 V source,

(ii) the voltage across the 6 ohm resistor. <img src='./qimages/10230-3b.jpg'>

4.(a) State and explain Kirchhoff's voltage and current laws.

(b) Compare primary and secondary cells.

5.(a) Derive the relations for conversion from delta to star connection for three-phase impedance.

(b) State and explain superposition theorem with the help of a suitable example.

6.(a) A coil with 250 turns carries a current of 2 and produces a flux of 0·3 mWb. When this current is reduced to zero in 2 ms, the voltage induced in a nearby coil is 60 volts. Calculate the self-inductance of each coil.

(ii) mutual inductance of coils. Assume coefficient of coupling 0.7.

(b) Give the comparison between electric and magnetic circuit.

7. Write short notes on any four of the following: Advantages of 3-phase over 1-phase system Reluctance Lenz's Law Hysteresis Loop Fleming's Right-Hand Rule Series Resonance