University of Pune 2010 B.Tech Electrical and Electronics Engineering Basic Electrical Engineering - exam paper
Basic Electrical Engineering
Total No. of Questions : 12] [Total No. of Printed Pages : 4
F. E. (Semester - I) Examination - 2010 BASIC ELECTRICAL ENGINEERING (2008 Pattern)
Time : 3 Hours] [Max. Marks : 100
Instructions :
(1) Answers to the two sections should be written in separate answer-books.
(2) Answer Q. No. 1 or Q. No. 2, Q. NO. 3 or Q. No. 4, Q. No. 5 or Q. No. 6, Q. No. 7 or Q. No. 8, Q. No. 9 or Q. No. 10 and Q. No. 11 or Q. No. 12.
(3) Figures to the right indicate full marks.
(4) Neat diagrams must be drawn wherever necessary.
(5) Use of non-programmable pocket size scientific calculator is permitted.
(6) Assume suitable additional data, if necessary.
Q.l) (A) What is Insulation Resistance ? State its unit and obtain an
expression for Insulation Resistance of the Cable. [08]
(B) With neat sketch explain Construction and Working of Lead
Acid Cell. [08]
OR
Q.2) (A) A resistance element having cross-sectional area of 10 mm2 and length of 10 meter takes a current of 4 Amp from 200V supply at temperature of 25C. Find (i) resistivity of the material and (ii) current it will take when temperature rises to 75C. Assume a25 = .0003/C. [06]
If a, and a2 are the two resistance temperature coefficients at t1 C and t2C, then prove that (a, - a2) = a, a2 (t2 - tj). [06] State applications of Nickel-Iron Cell and Nickel-Cadmium Cell. [04]
State and explain Superposition Theorem as applied to Simple DC Circuit. [06]
(B)
(C)
Q.3) (A)
(B)
(C)
State and explain Kirchoffs Laws. [04]
Determine resistance between (x) and (y) for the circuit shown
Fig. 1
State and explain Maximum Power Transfer Theorem. [06]
Q.4) (A)
(B)
Apply Thevenins Theorem to the circuit show in fig. 2 to calculate current in 01C2 resistance : [10]
8Q 9Q
Fig. 2
Q.5)
(A)
(B)
[08]
[10]
Compare Electric and Magnetic Circuit. Write short notes :
(a) Magnetic Leakage and Fringing.
(b) Energy stored in a Magnetic Field.
OR
Q.6) (A) Explain what do you mean by Statically Induced emf and
Dynamically Induced emf ? [06]
(B) A steel ring of 25 cm mean diameter and of circular cross-section 3 cm diameter has an air gap of 1.5 mm length. It is wound uniformly with 700 turns of wire carrying a current of 2 Amp. Calculate :
(a) MMF
(b) Flux Density
(c) Reluctance and
(d) Relative Permeability of Steel Ring [12]
SECTION - II
Q.7) (A) Define w.r.t. alternating quantities : [09]
(a) Instantenous Value
(b) Waveform
(c) Cycle
(d) Amplitude
(e) Periodic Time
(f) Frequency
(B) Sketch Waveforms of Currents and find its rms value and
average value for the equation : [08]
(a) i] = 15 sin (314.159 t) and
(b) i2 = 10 sin (314.159 t - tt/2)
OR
Q.8) (A) Prove that rms value of the sinusoidal alternating current is 0.707
times its maximum value. [06]
(B) Derive expression for energy stored in a capacitor. [06]
(C) Two capacitors of 50jlF each are connected in parallel with each other and this combination is connected in series with two capacitors of 80|JLF of 40|iF each. Calculate equivalent capacitance of the circuit. [05]
Define and explain following terms : [08]
(a) Active Power
Q.9) (A) (B)
Q.10) (A)
(B)
Q.ll) (A)
(B)
Q.12) (A)
(B)
(b) Reactive Power
(c) Impedance
(d) Admittance
A C ircuit consisting of Resistance of 20"2 and Inductance of
0.1 Henry is connected in series across single phase 200V,
50 Hz supply. Calculate :
(a) Current Drawn
(b) Power Consumed
(c) Draw relevant Phasor Diagram [09]
OR
A Coil of Resistance 50Q and Inductance of 0.1 H is connected in parallel with a branch which consists of resistance of 45Q in series with a capacitor of 100 (IF across a single phase 230V, 50Hz supply. Calculate Current, Power and p.f. of the Circuit. [09]
If a sinusoidal voltage of \> = Vm sinwt is applied across R-C series circuit, derive expression for current drawn and power consumed. Draw their waveforms also. [08]
Write short notes : [08]
(a) Losses taking place in Transformer
(b) An Autotransformer
Draw a complete phasor diagram for a 3 phase delta connected inductive balanced load supplied for 3-phase symmetrical A.C. supply. State equation for Active Power and Reactive Power consumed by Load. [08]
OR
A balanced Star Connected Load is supplied by 3-phase, 415V,
5 OH z supply. C urrent in phase is 2 0 Amp and iags 3 0 behind
its phase voltage. Find :
(a) Power Consumed by Load
(b) Circuit Parameters, and
(c) Load p.f. [08] Explain working principle of transformer and derive expression
for emf induced in its winding. [08]
[3861]-154/4
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