Indira Gandhi National Open University (IGNOU) 2005 B.Sc Physics Electrical Circuits & Electronics - Question Paper
BACHELOR OF SCIENCE (B.Sc.)
Term-End Examination
December, 2005
PHE-10
PHE-10 : ELECTRICAL CIRCUITS AND ELECTRONICS
Time : 2 hours Maximum Mar/cs : 50
Note ; Question no, 1 is compulsory. Attempt any four questions from the rest. Use of log tables and non-programmable calculators is allowed. Syrribois have their usual meanings,
2. (a) State and prove reciprocity theorem. 2+2
* (b) Draw the circuit diagram of a Wien-Bridge oscillator. Explain its working and write down the expression for output frequency. 6
3. (a) Draw and explain the I - V characteristics of a p - n
junction with external voltage. 5
(b) Design a T-pad attenuator to give an attenuation of
80 dB and to work on a line of .100 Q impedance. 5
4_ (a) Explain with the help of a suitable diagram how the two stages of an amplifier are coupJed using a resistance and a capacitor. How does this coupling affect the frequency response ? 5
(b) In a centre tap full wave rectifier, the load resistance,
Rl = 1*2 Each diode has a forward-bias dynamic resistance of 8 1. The voltage across half the secondary winding is 220 sin 314 t. Find the peak value, dc value, the rms value of the current, ripple factor and rectification efficiency. . 5
5. (a) Using IC 741 C operational amplifier draw the circuit diagram of the basic differentiator and obtain an expression for the output voltage. 5
(b) Using an IC LM 317, design an adjustable voltage
regulator for an output voltage of 5 V to 18 V. 5
6. (a) Convert decimal 872 to its BCD (8421) code
equivalent. 2
(b) Simplify the Boolean expression
Z = (B + Cj (B + Q + (A + 8 + Cl 3
(c} Design a MOD-6 counter using JK flip-flop and
explain its working. - 5
7* (a) Explain the concept of feed-back in an op-amp with the help of a suitable diagram, What do you understand by positive and negative feed-backs ? Ust one application of each- 5
(b) Explain the working of a cathode ray oscilloscope with the help of a block diagram. List two of its applications. 5
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