## BASIC ELECTRICAL ENGINEERING JNTU previous years question papers

**2010**

**BASIC ELECTRICAL ENGINEERING**

**(COMMON TO CSE, IT)**

**Time: 3hours Max.Marks:75**

**Answer any FIVE questions**

**All questions carry equal marks**

1.a) Explain the basic circuit components.

b) Three resistances 2 ohms, 4 ohms and 6 ohms are connected in series across 24V supply. Find the voltages across three resistors. [7+8]

2.a) State and explain Superposition theorem.

b) Write short notes on star – delta transformation. If Rab, Rbc and Rca are connected in delta, derive the expressions for equivalent star connection. [7+8]

3.a) Show that power dissipated by a pure inductor exited by a sinusoidal voltage source

V = Vm Sin ωt is Zero.

b) An alternating current is expressed as I = 14.14 Sin 314t.

Determine:

i) RMS current ii) Average current

iii) Form factor iv) Peak factor. [7+8]

4.a) Explain the constructional details of Transformer.

b) A 100 kVA, 1000/10000 V, 50 Hz, Single phase transformer has an iron loss of 1100 W. The copper loss with 5 A in the high voltage winding is 400 W. Calculate the efficiency

at 25 %, 0.8 Power factor. The out put terminal voltage being maintained at 10000 V.

[7+8]

5.a) Derive the emf equation of a DC generator.

b) A 4 – pole DC shunt generator with lap connected armature supplies a load of 100 A at 200 V. The armature resistance 0.1 ohms and the shunt field resistance is 80 ohms find the

i) Total armature current

ii) Current per armature path

iii) Emf generated. [7+8]

6.a) Explain the losses that occur in a DC machine.

b) A 200V DC shunt motor takes a total current of 100 A and runs at 750 rpm. The resistance of the armature winding and shunt field winding is 0.1 ohms and 40 ohms respectively. Find the total copper losses. [7+8]

7.a) Explain with the help of diagrams how a rotating magnetic field is produced in a 3 phase induction motor.

b) Three phase induction motor is wound for 4 – poles and is supplied from a 50 Hz supply.Calculate

i) The synchronous speed

ii) The speed of the motor when the slip is 3 %

iii) The rotor frequency. [9+6]

8. Explain the construction and operation of Moving iron repulsion type instruments with a neat diagram. [15]