question bank

1. B.E II Semester (CBCS) CSE
BASIC ELECTRICAL ENGINEERING (ES950EE)
Question Bank
UNIT-I
Short answer questions:
1. Derive the expression for rms value of sine wave?
2. Define active and reactive power?
3. Define rms and average value?
4. State Thevenin’s theorem and give utility of this theorem?
5. A coil has resistance of 10Ω and draws a current of 5A when connected across 100 volts, 50
Hz source. Determine the reactive power of circuit?
6. Define frequency and time period for sinusoidal source?
7. Calculate I1, I2 and I?

2. 8. State and explain Kirchoff’s current law?
9. Calculate RAB?
10. What do you
understand by mutual
inductance?
11. Explain dot
convention in
inductive circuits?

3. 12. Write expressions for active and reactive power.
13.
Long answer questions:
1. Calculate the effective resistance of the following combination of resistances and the voltage
drop across each resistance when a potential difference of 60 volts is applied between points A
and B.
2. (a) In the circuit given below obtain line and phase voltages and currents?

4. (b) Derive the expression for energy stored in a capacitor?
3. (a) Determine the current flowing through the 5Ω resistor by Thevenin’s theorem?
(b) An a.c sinusoidal source has an rms value of 40 A at 50 Hz frequency .write expression of
instantaneous current and obtain its value 0.002 sec after passing through maximum
positive value?
4. A resistance of 25Ω, inductance of 0.02H and capacitance of 120μF are connected in series
and fed from 220volts,50Hz supply. Determine inductive reactance, capacitive
reactance,
impedance current, active power, reactive power and power factor. Also draw the
phasor
diagram?
5. State and explain Thevenin’s theorem and Norton’s theorem with help of neat circuit diagrams
and their related expressions.
6. For the circuit below calculate impedance, current, p.f, VL,VR,VC also active power and
reactive power, draw the vector diagram?
7.
1) (a) Derive the expression for energy stored in an Inductor?
(b) For the circuit shown below find I1,I2,I3 using loop-current method?
2)
3)
4)
5)

5. 6) (a)
(b) Derive the expressions for energy stored in capacitance and inductance?
7) Find using Thevenin’s theorem the current in 5Ω resistor connected across AB in the network?
UNIT-II
Short answer questions:
1. Define voltage regulation of a transformer?
2. Explain principle of operation of auto transformer?
3. Give expression for regulation of a transformer?
4. Why transformer rating is in KVA?
5. Explain how power is transformed from one circuit to another circuit in 1-Ø
transformer?
6. Write the purposes of conducting a short circuit test on a single phase transformer?
7. Draw no load phasor diagram of a 1-ph transformer.
8. Give the basic principle of operation of a 1-phase transformer.
9. Name the losses in a transformer.
10. What do you mean by 3-Ø balanced load?
11. In a 3-Ø system what is difference between star and delta connection?
12. A balanced star connected load of (8+6j) Ω per phase is connected to 3-Ø, 230 volts,
and 50 Hz. Draw phasor diagram of above circuit?
13. What is the relationship between line and phase currents in balanced delta connected
system?
14. If the two readings of two wattmeters are W1 and W2 respectively. Write expression
for power factor.
15. A 100kVA transformer operating at full load at 0.8 p.f lagging. Its efficiency is 96%.

6. Calculate total losses of transformer.
16. Explain the no load operation of 1-phase transformer.
17. Draw the exact equivalent circuit of a transformer.
18.
Long answer questions:
1) (a) Explain the method of measuring 3-Ø power by two watt-meter method?
[dec 09]
(b)What is the purpose of O.C and SC test on a transformer?
2) (a)Explain the analysis of 3-Ø balanced circuits?[dec 09]
(b)Write short notes on Auto transformer?
3) A 50 KVA, 6600/200 volts transformer has a primary resistance of 10 Ω and a
secondary resistance of
0.01 Ω find
[june 2010]
(a) Total resistance reffered to secondary side
(b) Full load copper loss
(c) Efficiency of transformer at full load and UPF, if copper losses equal core
losses at this load?
4) Explain with neat diagram OC and SC tests on a single phase
transformer.Explain how can you draw the equivalent circuit with the help of above
tests? [may 2011]

7. 5) (a) A 25 KVA transformer has 500 turns on primary and 50 turns on the
secondary winding. The primary is connected to 3000 volts, 50 Hz supply. Find full
load and secondary currents, the secondary EMF’s and maximum flux in core?[may
12]
(b) Explain two-wattmeter method for measuring 3-Ø power with neat circuit
diagram?
6) (a) From fundamentals obtain the equivalent circuit diagram of transformers?
[may 13]
(b) Explain about auto transformer with necessary diagram?
7) The power in a 3-Ø circuit is measured by two-wattmeters, if input power is 100KW
and p.f is 0.66 lagging. What will be the reading of each wattmeter?
8) Explain in detail OC and SC tests of a single phase transformer with neat diagram.
Also explain how equivalent parameters and efficiency can be evaluated by these
tests? [june 14]
9) (a) Explain principle of operation of transformer on no-load? [jan 11]
(b) A transformer on no-load takes 4.5 A at a p.f of 0.25 lagging when connected to
a 230 volts, 50 Hz supply. The number of turns of primary winding is
250.calculate
i) The magnetising current
ii) The core loss
iii) Maximum value of flux in core
A balanced load of (8+6j) per phase is connected to 3-Ø, 230 volts, 50Hz
supply. Find current, power factor, real, reactive power and apparent power?
Prove that V=√3 Vph in 3-Ø star connection?

8. Deduce the expression for power in a 3-Ø balanced circuit in terms of line
voltage and line current?
UNIT –III
Short answer questions :
1. Give applications of series and compound motors? Dec 09
2. List out losses in DC motor? Dec 09
3. Draw the speed-torque, torque armature characteristics of a dc series motor?
[June 2010]
4. List out types of excitation employed for dc motors? june 10
5. Draw characteristics of DC series motors? [may 11]
6. Give applications of dc motors? may 11
7. What are functions of commutator in DC machine? may 12
8. What is function of back EMF in dc motor? Under what conditions it would be
zero? May 13
9. A dc shunt motor develops 10 h.p at 600 rpm when drawing a line current of 18A at
500 volts? Find torque? Jan 11

9. 10. Draw characteristics of shunt motors? Give applications of dc motors? Jan 12
Long answer questions:
1. (a) Describe the various methods of speed control of dc motor? [dec 09]
(b) Derive the EMF equation of generator?
2. Write short notes on DC shunt motors? Dec 09
3. (a) Explain principle of operation of a D.C generator? June 10
(b) Discuss the various methods of speed control of DC motor?
4. (a) Derive the EMF equation of a DC generator? May 11
(b) A 400 volt dc shunt motor takes 5A at no load. Its armature and field resistances
are 0.5 Ω and 200 Ω respectively. Calculate the efficiency of the motor when motor
takes 40 A on full load?
5. (a) Explain speed control of DC shunt motor with neat circuit diagram?[may 12]
(b) Explain various types of excitations for DC generators?
6. (a) Explain various speed control methods of DC motor? [may 13]
(b) Derive EMF equation of DC machine?
7. Explain in detail constructional details and principle of operation D.C generator.
Also derive the EMF equation of D.C machine? [june 14]

10. UNIT-IV
Short Answer Questions:
1. Draw speed-torque characteristics of an 3-phase induction motor.[june 2010]
2. Give reason why 3-phase induction motor cannot run at synchronous speed.[june 2014]
3. Mention the various types of 3-ф Induction Motors.[may 2012]
4. Mention various losses in a 3-phase induction motor.[may 2013]
5. Define slip and rotor current frequency.[may 2013]
6. What are the different types of starters used for 3-ф Induction Motors?[dec 09]
7. Give various types of speed control of 3-ф Induction Motors.[jan 2012]
Long Answer Questions:
1. (a) Explain how production of rotating magnetic field is produced in 3-phase
induction motor.[june 2014]
(b) Explain any one method of starting of 3-phase induction motor with neat schematic
diagram.
2. a) Explain the principle and operation of 3-ф Induction Motor.[may/june 2012]
b) Explain the various methods of starting 3-ф Induction Motors.
3. Explain constructional details and principle operation of 3-phase induction motor.
[may 2011]
4. what are the different methods of Speed control employed for 3-ф induction
motors.Explain?[dec 2009]
5. (a) Explain how production of rotating magnetic field is produced in 3-phase induction
motor?[jan 2011}
(b).Derive the torque equation of induction motor?
6.(a) Explain star-delta starting of 3-phase induction motor with neat schematic diagram.
[may 2013]

11. (b) Explain constructional details and principle operation of 3-phase induction motor.
UNIT-V
Short Answer Questions:
1. Why 1-phase induction motor are not self starting.
2. Compare conventional DC motor and brushless DC motor.
3. Where and why is a centrifugal switch used in a split phase motor?
4. How can the direction of rotation of capacitor start motor be reversed?

12. 5. How are the 1- Induction motors made self starting?ϕ
6. What are the basic features of split-phase motors?
Long Answer Questions:
1. a) Explain capacitor run motor with help of neat circuit diagram and mention its
application.
(b) Explain constructional details and working principle of stepper motor.
2. What are the different methods of speed control employed for polyphase Induction motor.
3. Explain the principle and operation of brushless D.C. motor?
4. Explain the following terms
a) 1- capacitor start motorϕ
b) Double field revolving theory
c) Stepper motor