Elements of Electrical Engineering — Winter 2018

Objective Question (MCQ) Mark

07 1. Akilowatt hour is the unit of [a] Energy [b] power [c] electric charge [d] electric current 2. An ideal voltage source should have [a] zero internal resistance [b] infinite source resistance [c] large value of e.m.f. [d] low value of e.m.f. 3. Awave completes one cycle in 10 µs. Its frequency will be [a] 10µHz [b] 50 Hz [c] 100 KHz [d] 10 KHz 4. If a pure capacitance is connected to an a.c. source, the current ____ the source voltage by ______ [a]Lags, 900 [b] lags, 450 [c] leads,900 [d] leads, 450 5. When two capacitors of 6µF and 12µF are connected in series, their effective value will be [a] 18 µF [b] 6 µF [c] 4 µF [d] µF 6. An R-Lcircuit has a resistance of 3 ohms and a reactance of 4 ohms. The impedance of the circuit is [a]5 ohms [b] 7 ohms [c] 1 ohm [d] 25 ohms 7. The total lumens emitted by a source of 1 candela are equal to [a]0.4π [b] 4π [c] 2π [d] 8π

07 1. Anetwork which does not have either voltage source or current source is called [a] Active network [b] Passive network [c] Resistive network [d] Dummy network 2. Conductivity is analogous to [a]Flux [b] reluctance [c] permeance [d] current 3. Tesla is the unit of [a]Flux density [b] flux [c] magnetic field strength [d] reluctance 4. The value of form factor is [a] 11.1 [b] 1.11 [c] 1.414 [d] 14.14 5. The area of hysteresis loop is a measure of [a] magnetic flux [b] permeance [c] mmf per cycle [d] energy loss per cycle 6. The conjugate of the complex quantity (4-j5) will be [a] -4-j5 [b] 4-j5 [c] -4+j5 [d] 4+j5 7. The power factor of R-Cseries a.c. circuit is [a] unity [b] lagging [c] leading [d] zero

State and explain Kirchoff’s voltage and current laws.

Define & explain temperature co-efficient of resistance.

Derive the equations to translate a passive electric circuits from star network to delta network configuration with diagram.

Derive the expression for the equivalent capacitance of capacitors connected in parallel.

Find out the equation for energy stored in capacitor.

The total capacitance of two capacitors is 0.03 Fwhen joined in series and 0.16 Fwhen connected in parallel. Find the capacitance of each capacitor.

State and explain faraday’s laws of electromagnetic Induction.

Give similarities and dissimilarities between electrical circuit and magnetic circuit.

Derive the equation of coefficient of coupling of magnetically coupled coils.

Explain magnetic hysteresis.

Acertain waveform has a form factor of 1.2 and a peak factor of 1.5. If the maximum value is 100, find the r.m.s. value and the average value. Prove the condition of resonance for series R-L-Ca.c. circuit. Also analyze the

phenomena with the help of graph.

Explain in brief the following for 3-phase AC circuit: Phase sequence, Line voltage, Phase voltage

Two circuits, the impedances of which are given as Z1=(10+j15)ohms and Z2=(6-j8) ohms are connected in parallel. If the total current supplied is 15A, what is power taken by each branch? Explain in brief power measurement using two wattmeter method in 3-phase

system with star connected load.

List the different types of illumination scheme.

Discuss the types of cables used for residential and commercial wiring. List the different types of lamp and explain florescent lamps with wiring

diagram.