BASIC ELECTRICAL AND ELECTRONICS ENGINEERING SUPPLY 2K7 RO5

1. (a) Determine the voltage

VAB in the circuit shown in the figure 1a Figure 1a (b) Find the power dissipated in 40 ohm resistor of figure 1b shown. [10+6] Figure 1b
2. (a) Derive the torque equation of a D.C motor. (b) A 4-pole wave wound D.C armature has 294 conductors. Find i. Flux per pole to generate 230 V at 1500 r.p.m. ii. Electromagnetic torque at this flux when armature current is 120 A.[8+8]
3. (a) Determine the range of input voltage that maintains an output voltage of 10 V at the output for the regulator shown in the figure 3a Figure 3a (b) Explain the applications of Zener diode. (c) Explain static and Dynamic Resistance of a diode. [4+8+4]
4. (a) The half wave rectifier shown in the figure 4a is fed with a sinusoidal voltage V=20 sin100t. i. Sketch the output waveform. ii. Determine the DC output voltage assuming ideal diode behaviour. iii. Repeat the calculations assuming the simplified diode (silicon) model. Figure 4a (b) Draw the circuit diagram of full wave rectifier having two diodes and explain its operation. [8+8]
5. (a) Sketch a family of drain and mutual characteristics and explain the shape of the curves qualitatively for a JFET. (b) For a source self-bias circuit if ID = 0.8 mA, IDSS = 1.65 mA and VP = –2V find VGS. [8+8]
6. (a) With the help of block diagrams, explain the four different feed back topologies. (b) Draw the circuit of a voltage series feedback amplifier with BJT. What is the effect of this feedback as Ri and R0. [6+10]
7. (a) Explain the operation of an integrator using OP-AMPs. (b) Distinguish between positive and negative feedbacks. (c) List out the characteristics of OP-AMP. [6+4+6]
8. (a) Realize Full-adder using logic gates. (b) Explain the principle of operation of D to A converter. (c) Simplify the following functions i. A′BC′ + A′C′D + A′B′D′ + AC + BCD′ ii. A′B′D′ + A′CD + A′BC.
SET :2
1. With a neat sketch explain the construction and working principle of moving iron (M.I) type instrument. Write down the torque equation. [16]
2. (a) Does the induction motor have any similarities with the transformer. Compare the similarities and differences between them. (b) A 20 h.p, 400 V, 50 Hz, 3-phase induction motor has an efficiency of 80% and working at 0.7 p.f. The motor is connected to 400 Volts, 3-phase supply calculate the current drawn by the motor from the mains. [8+8]
3. (a) For the network shown in the figure 3(a)i determine the range of RL and IL that will result in VRL being maintained at 10 V. i. Determine the maximum Wattage rating of the diode. Figure 3(a)i ii. The reverse saturation current of the diode is 1 μA. Its peak inverse Voltage is 500V. Find ri, Vo that PIV is not exceeded. show in figure 3(a)ii & figure 3(a)iii Figure 3(a)ii Figure 3(a)iii
4. (a) A sinusoidal voltage of peak value 40V and frequency 50 Hz is applied to HWR using PN diode. The total load resistor is 800 . Neglecting cut in voltage and using idealized characteristic for the diode with Rf=8 and Rr=α calculate i. Peak D.C and RMS values of load current ii. D.C and A.C output power iii. Rectifier efficiency iv. Ripple factor. (b) Derive the formulas used in the above problem. [8+8]
5. (a) Draw the static drain characteristics and transfer characteristics of an N- channel MOSFET and explain the shape of the curves qualitatively. (b) Explain the following i. BJT Switching times with suitable sketches. ii. Early effect and its consequences. [6+10]
6. (a) Classify and define the amplifiers depending on the conduction period and sketch the input and output waveforms. (b) Show that the maximum theoretical efficiency of a class A power amplifier is 50%. [8+8]
7. (a) Find the resistance R and hfe for the transistor to provide a resonating frequency of 5 kHz of a transistorized phase shift oscillator. The biasing resistances are 25 kand 47 k. The load resistance is 10. The capacitor in the tank circuit is 1000 pF which hie of the transistor is 2 k. (b) Explain the role of commutating capacitors in multivibrator circuits. (c) Design an Astable multivibrator circuit with 50% duty cycle and f=2 KHz, VCC=10V, VBE(Sat) = 0.6V, VCE(Sat) = 0.3V. Using N-P-N Si transistors. [6+2+8]
8. (a) Explain with a block diagram the major blocks of a digital computer. (b) Implement the following with either NAND or NOR gates. Use only 4 gates only the normal inputs are available. F = w′xz + w′yz + x′yz′ + wxy′z. (c) With a circuit diagram, explain Counter type A to D converter. [4+6+6]
SET :3
1. (a) Define resistance. (b) State and explain Ohms Law. (c) Find out the equivalent resistance of the following circuit between the points A and B (all values are in ohms) as shown in the figure 1c [2+4+4] (d) Find the impedance between ‘X’ and ‘Y’ points of the figure 1d shown.
2. (a) Give the constructional features of “CORE” and “Shell” types of transformers, and give the advantages and disadvantages of each type. (b) A 5 KVA, 2300 / 230 V, 50 Hz transformer was tested for the iron loss with normal excitation and copper losses at full load, and these were found to be 40 Watts and 112 Watts respectively. Calculate efficiency of the transformer at i. full load. ii. half full load. Assume the power factor of the load as 0.8. [8+8]
3. (a) Draw the equivalent circuits of i. ideal diode ii. Simplified model of diode. iii. piece wise linear model of diode. Draw their characteristics. (b) Derive the expression for diffusion capacitance in a diode. [10+6]
4. (a) The half wave rectifier shown in the figure 4a is fed with a sinusoidal voltage V=20 sin100t. i. Sketch the output waveform. ii. Determine the DC output voltage assuming ideal diode behaviour. iii. Repeat the calculations assuming the simplified diode (silicon) model. (b) Draw the circuit diagram of full wave rectifier having two diodes and explain its operation. [8+8]
5. (a) Compare and contrast FET and BJT. (b) Give the constructional features of JFET and explain its operation with the help of the drain characteristics. (c) From the drain characteristics derive mutual characteristic and explain the shape of the curve qualitatively. [6+6+4]
6. (a) Draw the circuit of a current shunt feedback amplifier and explain. (b) An amplifier has a gain of 10,000 without feedback. The gain is reduced to 50 with negative feedback. Find the feedback factor. (c) Explain the principle of operations of Tuned amplifiers.
7. (a) Draw the circuit diagram of Wien bridge oscillator using BJT. Show that the gain of the amplifier must be at least 3 for the oscillations to occur. (b) For the fixed-bias Ge transistor, n-p-n type, the junction voltages at saturation and cutoff one in active region, may be assumed to zero. This circuit operate properly over the temperature range -50 oC to 75 oC and to just start malfunctioning at these extremes. The various circuit specifications are: VCC = 4.5V, VBB = 3volts, hfe=40 at -50 oC, and hfe=60 at 75 oC, ICBO = 4 μA at 25 oC and doubles every 10 oC. Collector current is 10 μA. Design the values of Rc1, R1 and R2. [8+8]
8. (a) Explain how a shift register is used as a Ring counter. Draw the O/P waveformfrom each flip-flop of a 3-stage unit. (b) Prove that if w′x + yz = 0, then wx + y′ (w′+z′) = wx + xz + x′z′ + w′y′z. (c) Represent the given negative numbers in sign-magnetude, 1’S and 2’S com- plement representation in 12-bit format. i. –64 ii. –512.
SET :4
1. Consider a general A.C circuit in which the current leads the applied voltage by an angle φ. Write the equation for the voltage and current and hence derive the equation for the power. Also plot the voltage, current and power wave forms. [16]
2. (a) Why is the core of the transformer laminated? (b) What are the various losses in a transformer? And how do these losses vary? (c) A single phase 50 Hz transformer has 100 turns on the primary and 400 turns on the secondary. The cross sectional area of the core is 250 cm2. The primary winding is connected to 230 Volts. Determine i. E.M.F induced in the secondary winding. ii. The maximum value of the flux density in the core. [4+8+4]
3. (a) Draw the V-I characteristics of p-n diode and explain. (b) i. What is the current in the diode shown in the figure
3(b)i ii. Calculate the load voltage, load power, diode power and total power in the above circuit. (c) Explain how p-n junction diode act as a rectifier.
4. (a) The half wave rectifier shown in the figure 4a is fed with a sinusoidal voltage V=20 sin100t. i. Sketch the output waveform. ii. Determine the DC output voltage assuming ideal diode behaviour. iii. Repeat the calculations assuming the simplified diode (silicon) model. (b) Draw the circuit diagram of full wave rectifier having two diodes and explain its operation.
5. (a) Give the equivalent circuit of UJT and explain its operation with the aid of equivalent circuit. What is intrinsic stand off ratio? Explain its significance.
(b) A transistor with β = 100 is used in CE configuration with collector to base bias. If Rc = 1K , Vcc = 10 V, VBE=0 V and VCE = 4 V. Find the value of RB and stability factor S.
6. (a) List out different distortions that occur in amplifiers and discuss.
(b) Enumerate the effect of negative feedback on the various characteristics of the amplifier.
(c) Draw the circuit diagram of an emitter follower circuit and mention what type of feedback is employed? Justify your answer.
7. Define the following terms with reference to OP-AMPs:
(a) i/p bias current
(b) i/p offset current
(c) open loop gain
(d) i/p off set voltage
(e) o/p offset voltage
(f) CMRR
(g) PSSR
(h) Skew rate.
8. (a) Realize Exclusive OR gate using minimum number of NAND gates.
(b) Realize SR flip-flop using NAND gates.
(c) Explain the principle of decade counter and realize it using JK-flip-flops.
(d) Realize exclusive OR gate using basic gates