## Basic Electrical Engineering (BEE) - Dec 2013

### First Year Engineering (Semester 1)

TOTAL MARKS:

TOTAL TIME: HOURS

### Answer any one question from Q1 & Q2

**1 (a)** Define Insulation Resistance and derive expression for it of a Cable.(6 marks)
**1 (b)** A single core cable has its conductor diameter as 2 cm and outer diameter as 5 cm. The resistivity of conductor and insulator are 1.73 ? 10^{-8} ? -m and 8?10^{12}? -m respectively. Calculate resistance of conductor and insulation for a cable of 100 meter.(6 marks)
**2 (a)** Derive an expression for Energy stored in a magnetic field.(6 marks)
**2 (b)** An iron ring of mean circum ference of 50 cm has an airgap of 2mm cut in it. It has circular cross section with area of 5 cm^{2}. It carries a coil wound with 600 turns wound uniformly. The relative permeability of iron is 580. If the coil carries a current of 2 amp. Find the Flux in air gap.(6 marks)

### Answer any one question from Q3 & Q4

**3 (a)** Derive an expression of Average value of an alternating simusoidal current.(6 marks)
**3 (b)** An inductive coil, having negligible resistance and 0.1 H inductance, is connected across a 200V, 50Hz supply. Find

(i) Inductive reactance.

(ii) RMS value of current drawn. State equations for voltage & current.(6 marks)
**4 (a)** Compare core type and shell type transformer construction.(6 marks)
**4 (b)** A 25k VA, 2200/20V 50Hz single phase transformer has a primary resistance of 1.8 ? and secondary resistance of 0.02 ?. Calculate the transformer efficiency at half load 0.8 lagging p.f. The Iron Losses are 1000 watt.(6 marks)

### Answer any one question from Q5 & Q6

**5 (a)** A circuit, consisting of resistance of 20 ? and inductance of 0.1 H in series, is connected across single phase 220V, 50Hz supply.

Calculate :

(1) Current drawn

(2) p.f. and

(3) Power consumed by ckt.(7 marks)
**5 (b)** Define:

(1) Impedance and

(2) Admitance of circuit. Sketch the impedance & admittance triangles.(6 marks)
**6 (a)** Three coils each of 5? resistance and 6? inductive reactance are connected in Delta across 3 phase, 440V, 50Hz, A.C. Supply. Calculate current drawn p.f. of system and power consumed by circuit.(7 marks)
**6 (b)** A coil of 2? resistance and 0.01 H inductance is connected in series with a capacitor across 200V supply. What must be capacitance in order that maximum current is drawn at frequency of 50 Hz. Find also voltage across capacitance.(6 marks)

### Answer any one question from Q7 & Q8

**7 (a)** State and explain kirchhoff?s laws.(8 marks)
**7 (b)** Calculate the equivalent resistance between terminals X and Y for the circuit shown in Fig, 1

**8 (a)**Apply Thevenin's theorem to calculate current flowing in branch A-B as shown in Fig. 2 (8 marks)

**8 (b)**State and explain Superposition Theorem.(5 marks)