Elements of Electrical Engineering — Summer 2023

Objective Question (MCQ) Mark

07 1. The unit of inductive reactance is

Ohm (b) henry (c) joule (d) ohm.m 2. The “Superposition theorem” is essentially based on the concept of

duality (b) linearity (c) reciprocity (d) non-linearity 3. The power factor of a purely resistive circuit is

Zero (b) lagging (c) unity (d) leading 4. The power taken by a 1-phase load is given by the expression

3VICosɸ (b) VICosɸ (c) VISinɸ (d) 3VISinɸ 5. The Q-factor of a coil is given by

Its power factor Cosɸ (b) ratio R/Z (c) reciprocal of its power factor

ratio of maximum energy stored and energy dissipated per cycle 6. In an ac circuit, the ratio of kW/kVA represents

Power factor (b) load factor (c) form factor (d) diversity factor 7. The frequency of DC supply is ____

50 Hz (b) 25 Hz (c) 100 Hz (d) Zero

07 1. Thevenin’s equivalent circuit consists of ____

Series combination of R , Eand R TH TH L

Series combination of R , E TH TH

Parallel combination of R , ETH TH

Parallel combination of R , Eand R TH TH L 2. The r.m.s. value of sinusoidal 100 Volt peak to peak is ____ Volt.

50 (b) 100 (c) 50/√2 (d) 100/√2 3. The power factor at resonance in R-L-Ccircuit is

Unity (b) Zero (C) leading (d) lagging 4. Watt.hour is the unit of

Electric capacity (b) Electric charge (c) Electric power (d) Electric energy 5. The unit of specific resistance is ___

Ohm (b) Ohm.m2 (c) Ohm.m (d) Ohm2.m 6. Abattery is a source of

1-phase AC voltage (b) 3-phase AC voltage (c) DC voltage (d) AC or DC voltage 7. Three capacitors of value of 8 µF, 16 µF and 32 µF are connected in series, the total capacitance will be

56 µF (b) 32 µF (c) 7.32 µF (d) 32/7 µF

State and explain Coulomb’s laws.

Compare similarities and dissimilarities between electrical and magnetic circuit.

Two capacitors of 4 µF and 8 µF are connected in series and charged from a constant voltage of 210 Vsupply. Calculate : (a) The voltage across each capacitor (b) The charge on each capacitor.

Explain the factors affecting the resistance of a conducting material.

Derive the equation for the co-efficient of coupling of two magnetically coupled coils Aand B.

Three resistances R , Rand Rare connected in delta. Obtain expressions for AB BC CA their equivalent star resistances

Discuss different methods of representation of vector quantities.

Explain different types of capacitors in brief.

State and explain self inductance (L). Derive expression of co-efficient of mutual coupling between two coils having inductance of Land L .12

Explain : (a) Form factor and (b) Peak factor.

Derive the equation of energy stored in a Capacitor.

Aseries RLC circuit when R = 10Ω , L = 10mH and C =1 µF has an applied voltage of 200 Vat resonant frequency. Calculate the resonant frequency, the current in the circuit and voltage across the element at resonance. Find the Q-factor and bandwidth.

Define: (i) R.M.S. Value (ii) Form factor (iii) Amplitude factor

Acapacitor is charged with 5000 µC. If the energy stored is 1 joule then find:

Voltage and (b) Capacitance.

What is the need of earthing? Explain the different methods of earthing.

Discuss staircase wiring with simple diagram.

Give the circuit diagram of ELCB. Explain its working and applications.

Obtain the relationship between line and phase values of current in a three phase, balanced, delta connected system.