This document contains an exam for a basic electrical engineering diploma. It consists of two parts: Part A contains 10 multiple choice questions worth 4 marks each, and Part B contains 4 long-form questions worth 10 marks each. The questions cover topics like Ohm's law, resistor circuits, electric power, heating effects, magnetism, electromagnetic induction, capacitors, and more. The exam is worth a total of 80 marks and lasts 3 hours.

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C14–EE–106
4046
BOARD DIPLOMA EXAMINATION, (C–14)
OCT/NOV—2016
DEEE—FIRST YEAR EXAMINATION
BASIC ELECTRICAL ENGINEERING
Time : 3 hours ] [ Total Marks : 80
PART—A 4×10=40
Instructions : (1) Answer all questions.
(2) Each question carries four marks.
1. (a) List any two limitations of Ohm’s law. 2
(b) Define the terms conductance and conductivity. 2
2. (a) Write the expression for equivalent resistance when three
resistors are connected in parallel. 2
(b) What are the factors on which the resistance of a conductor
depends? 2
3. (a) Give the expression and unit of electrical power. 2
(b) Define electrical energy and give its unit. 2
4. (a) State Joule’s law of heating. 2
(b) List any four applications of heating effects of electric
current. 2
5. (a) State right-hand thumb rule. 2
(b) Give expression for field strength (i) at the centre of circular
conductor and (ii) at any point on the axis of a circular
conductor. 2
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6. (a) State Fleming’s left-hand rule. 2
(b) Define magnetic flux and magnetic flux density. Mention
their units. 2
7. (a) State Faraday’s 1st law of electromagnetic induction. 2
(b) A coil of 250 turns is linked with a flux of 0·025 Wb, when
carrying a current of 25 A. Calculate the inductance of the
coil. 2
8. (a) State Lenz’s law. 2
(b) Write the expressions for the self-inductance and mutual
inductance. 2
9. (a) State Coulomb’s 2nd law of electrostatics. 2
(b) List any four uses of a capacitor. 2
10. (a) Write an expression for energy stored in a capacitor. 2
(b) Plot electrostatic field due to isolated positive charge and
isolated negative charge. 2
PART—B 10×4=40
Instructions : (1) Answer any four questions.
(2) Each question carries ten marks.
11. (a) Calculate the length of copper wire 1·5 mm in diameter to
have a resistance of 0·3 ohm, given that resistivity of copper
is 0·017 m W-m. 4
(b) The resistance of a coil of wire increases from 40 ohms at
10 ºC to 48·25 ohms at 60 ºC.
(i) Find the temperature coefficient of resistance at 0 ºC
(ii) Find the resistance of coil at 0 ºC 6
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12. (a) Distinguish among conductor, insulator and semi-
conductor w.r.t valance electrons and give examples. 4+1=5
(b) Two resistances 50 ohms and 10 ohms are connected in
parallel and draw a current of 20A from the supply.
Determine the current in each branch and supply voltage. 5
13. (a) Calculate the input of an electric motor when the output is
10 HP and the efficiency of the motor is 90%. 3
(b) Calculate electricity bill for the month of June at R 1·20 per
unit for a residential building with the following loads. The
meter rent per month is R 20 : 7
(i) 10 Nos. of 40 watt tubelights used for 10 hr/day
(ii) 8 Nos. of 80 watt fans used for 12 hr/day
(iii) 1 No. of 250 watt refrigerator used for 12 hr/day
(iv) 1 No. of 1000 watt heater working for 1hr/day
(v) 1 No. of 450 watt electric iron working for 1 hr/day
14. (a) Define thermal efficiency. 2
(b) The heater element of an electric kettle has a constant
resistance of 100 ohms and the applied voltage is 250 V.
Calculate the time taken to raise the temperature of
one litre of water from 15 ºC to 90 °C, assuming that 85%
of the power input to the kettle is usefully employed, if the
water equivalent of the kettle is 100 grams. 8
15. (a) A straight long conductor of 1 meter length carrying a
current 60 A is placed at right angle to a uniform magnetic
field to strength 2·5 Wb/m2
. Determine the mechanical
force acting on the conductor. 3
(b) A circular iron ring having a mean diameter of 30 cm and
cross-sectional area of 4 cm2
is uniformly wound with 1000
turns of wire. A radial saw cut of 1 mm is made in the ring.
Determine the current which will produce a flux of
0·4 m-Wb in the air gap. Assume the relative permeability
under these conditions to be 941. Neglect leakage and
fringing. 7
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16. (a) Explain the concept of self-induced e.m.f. 5
(b) The combined inductances of two coils connected in series
are 0·6 H and 0·1 H. Depending on the relative directions of
the currents in the coils, if one of the coils, when isolated,
has a self-inductance of 0·2 H, calculate—
(i) the mutual inductance;
(ii) the coupling coefficient. 5
17. (a) Derive an expression for energy stored in a magnetic field. 5
(b) An iron ring has a cross-section of 20 cm2
and a mean
length of 120 cm is wound with 300 turns. The
permeability of iron is 800. If the current in the coil is 10 A,
calculate—
(i) the inductance;
(ii) energy stored in joules. 5
18. (a) Three capacitors of 2 micro-farad, 4 micro-farad and 6
micro-farad are connected in series across a 220-V d.c.
supply.
(i) Find the total capacitance.
(ii) Find charge on each capacitor.
(iii) Find potential difference across each capacitor. 6
(b) Two small balls having charges one double the other are
placed at a distance of 0·5 m apart in air. If the repulsive
force between the balls is 2·75 N, determine the charge on
each ball. 4
H H H
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