Questions for circuit debugging, These questions are custom designed by Bhushan and Adhithya to test your understanding. Only if you understood the concepts you will be able to answer these questions. These questions were framed for Coloumb 2022 a symposium conducted by Rajalakshmi engineering college Thandalam, Chennai.

1. ROUND 1(Set A)
NAME:
DEPT:
COLLEGE:
1. What is the maximum possible speed of the transformer in R.P.M?
2. The boolean expression for P is
3. The voltage across a forward biased Si diode is
(a) 0.3 V
1

2. (b) 0 V
(c) 0.7 V
(d) Dependent on the bias voltage.
4. Match the following
Thermistor Mechanical force
Photoconductive cell Temperature
Strain gauge Light
5. Which of the following according to KVL must be zero?
(a) Algebraic sum of currents in closed-loop
(b) Algebraic sum of power in closed-loop
(c) Algebraic sum of losses in closed-loop
(d) Algebraic sum of voltages in closed-loop
6. The n-region in a PNP transistor is
(a) base
(b) collector
(c) emitter
(d) case
7. Name any 3 commonly used number systems in digital electronics
8. Two currents that are nearly the same in normal operation of the transistor are
(a) collector and base
(b) collector and emitter
(c) base and emitter
(d) input and output
9. What happens if in an OP-AMP the Feedback resistor is open? Assume negative
feedback configuration
2

3. 10. If the current in a coil is AC, the amplitude of MMF is of the nature
(a) varies with time but not with space
(b) varies with space but not with time
(c) varies with both space and time
(d) doesn’t vary with both space and time
11. A sound wave has a frequency of 250Hz. What is its time period?
12. The process of adding impurity atoms to a pure semiconductor is called?
(a) Recombination
(b) Crystallization
(c) Doping
(d) Bonding
13. For the given op-amp configuration, find the value of feedback resistor
14. A Thermocouple
(a) Produces a change in resistance for a change in temperature
(b) produces a change in voltage for a change in temperature
(c) is made of two dissimilar metals
(d) Both (b) and (c)
3

4. 15. Which of the following will happen in a transformer when the number of sec-
ondary turns is less than the number of primary turns?
(a) The voltage gets stepped up
(b) The voltage gets stepped down
(c) The power gets stepped up
(d) The power gets stepped down
16. Find Output voltage Vo of the following circuit.
17. Find the current through the 4 Ω resistor.
4

5. 18. What is the unit of resistivity?
(a) Ohms
(b) Mho meter
(c) Mho
(d) Ohm meter
19. Determine the output waveform of the following circuit when the input is a 50Hz
Sine wave.
20. Find the correct correct bridge rectifier
5

6. Round 1 (Set A) Answer key
1. What is the maximum possible speed of the transformer in R.P.M?
Zero RPM, It is a static device.
2. The boolean expression for P is
Option (A) A.B
3. The voltage across a forward biased Si diode is
(a) 0.3 V
(b) 0 V
(c) 0.7 V
(d) Dependent on the bias voltage.
1

7. 4. Match the following
Thermistor Temperature
Photoconductive cell Light
Strain gauge Mechanical force
5. Which of the following according to KVL must be zero?
(a) Algebraic sum of currents in closed-loop
(b) Algebraic sum of power in closed-loop
(c) Algebraic sum of losses in closed-loop
(d) Algebraic sum of voltages in closed-loop
6. The n-region in a PNP transistor is
Base
7. Name any 3 commonly used number systems in digital electronics
(a) Octal
(b) Binary
(c) Hexadecimal
(d) Decimal
8. Two currents that are nearly the same in normal operation of the transistor are
(a) collector and base
(b) collector and emitter
(c) base and emitter
(d) input and output
9. What happens if in an OP-AMP the Feedback resistor is open? Assume negative
feedback configuration
The output waveform saturates (Square wave)
10. If the current in a coil is AC, the amplitude of MMF is of the nature
2

8. (a) varies with time but not with space
(b) varies with space but not with time
(c) varies with both space and time
(d) doesn’t vary with both space and time
11. A sound wave has a frequency of 250Hz. What is its time period?
T =
1
250
= 0.004 Sec = 4 ms
12. The process of adding impurity atoms to a pure semiconductor is called?
(a) Recombination
(b) Crystallization
(c) Doping
(d) Bonding
13. For the given op-amp configuration, find the value of feedback resistor
ACL = 1 +
Rf
R1
50 = 1 +
Rf
1 × 103
Rf = 49kΩ
14. A Thermocouple
(a) Produces a change in resistance for a change in temperature
(b) produces a change in voltage for a change in temperature
3

9. (c) is made of two dissimilar metals
(d) Both (b) and (c)
15. Which of the following will happen in a transformer when the number of sec-
ondary turns is less than the number of primary turns?
(a) The voltage gets stepped up
(b) The voltage gets stepped down
(c) The power gets stepped up
(d) The power gets stepped down
16. Find Output voltage Vo of the following circuit.
Vo = −(2 + 3 + 4) = −9V
This is an inverting summer so the output is inverted.
17. Find the current through the 4 Ω resistor.
(a) find the equivalent resistance by applying series parallel concept, R =3.334 Ω
(b) find the total current, I =4.799 A
(c) by current division rule, I4Ω =3.19 = 3.2 A
4

10. 18. What is the unit of resistivity?
(a) Ohms
(b) Mho meter
(c) Mho
(d) Ohm meter
19. Determine the output waveform of the following circuit when the input is a 50Hz
Sine wave.
Cosine wave
Since it is a differentiator.
5

11. 20. Find the correct correct bridge rectifier
Option D
6

12. ROUND 1(SET B)
NAME:
DEPT:
COLLEGE:
1. In the given logic circuit, the output Y is
2. In the given network, find the current i1
1

13. 3. Find the voltage across the resistor
4. Identify the Forward Biased Diode(s)
(a) D1
(b) D2
(c) D3
(d) D1 and D3
2

14. 5. If a single diode in centre-tapped full-wave rectifier opens,the output will be
(a) 0V
(b) half-wave rectified
(c) reduced in amplitude
(d) unaffected
6. When the positive lead of an ohmmeter is connected to the cathode of the diode
and the negative lead is connected to the anode of the diode,the meter reads
(a) very low resistance
(b) infinitely high resistance
(c) high resistance initially, decreasing to about 100Ω
(d) gradually increasing resistance
7. The process of changing the half-wave or full-wave rectified voltage to a constant
DC voltage is called
(a) filtering
(b) AC to DC conversion
(c) damping
(d) ripple suppression
8. If the base current for a transistor operating below saturation is increased,the
collector current
(a) increases and the emitter current decreases
(b) decreases and the emitter current decreases
(c) increases and the emitter current does not change
(d) increases and the emitter current increases
9. For normal operation of a NPN transistor,the base must be
(a) disconnected
(b) negative with respect to the emitter
(c) positive with respect to the emitter
(d) positive with respect to the collector
3

15. 10. A certain non-inverting amplifier has an Ri of 1 kΩ and an Rf of 100 kΩ, If the
feedback resistor is suddenly removed from the circuit, the voltage gain of the
amplifier
(a) decreases
(b) zero
(c) increases
(d) remains the same
11. Which of the following elements of electrical engineering cannot be analyzed
using Ohm’s law?
(a) Capacitors
(b) Inductors
(c) Transistors
(d) Resistance
12. A 2mH, a 3.3mH, and a 0.2mH inductor are connected in series. The total
inductance is
(a) 5.5mH
(b) less than 5.5mH
(c) less than 0.2mH
(d) 55mH
13. Which of the following statements is correct?
(a) Flux is Directly proportional to current
(b) Flux is Inversely proportional to current
(c) Flux is Directly proportional to voltage
(d) None of the above
14. Stator of an alternator consists of
(a) An iron core.
(b) Stator core.
(c) Both (a) and (b)
(d) None of the above.
4

16. 15. A resistor is connected across a 50 V source. What is the current in the resistor
if the color code is red, orange, orange, silver?
(a) 21.4 mA
(b) 214 mA
(c) 2.2 mA
(d) 2 mA
16. Most widely used motor is
(a) Double cage induction motor
(b) Slip ring induction motor
(c) Squirrel cage induction motor
(d) Synchronous motor
17. What is the maximum possible speed of the transformer in R.P.M?
18. An infinite Bus bar has
(a) Constant voltage
(b) Constant frequency
(c) Constant Current
(d) Both (a) and (b)
19. Determine the type of filter implemented using Op-amp in the given circuit
diagram
5

17. 20. Anabhayan uses a single phase induction motor for watering his crops. His
motor is not starting! What could be the issue?
(a) Low quality motor.
(b) Capacitor failure.
(c) Pump air-locked.
(d) Frequency is fluctuating.
6

18. ROUND 1(Set B) ANSWER KEY
1. In the given logic circuit, the output Y is
option D
2. In the given network, find the current i1
1

19. 15 mA
3. Find the voltage across the resistor
11.3 V
4. Identify the Forward Biased Diode(s)
(a) D1
(b) D2
(c) D3
(d) D1 and D3
5. If a single diode in centre-tapped full-wave rectifier opens,the output will be
(a) 0 V
(b) half-wave rectified
(c) reduced in amplitude
(d) unaffected
2

20. 6. When the positive lead of an ohmmeter is connected to the cathode of the diode
and the negative lead is connected to the anode of the diode,the meter reads
(a) very low resistance
(b) infinitely high resistance
(c) high resistance initially, decreasing to about 100Ω
(d) gradually increasing resistance
7. The process of changing the half-wave or full-wave rectified voltage to a constant
DC voltage is called
(a) filtering
(b) AC to DC conversion
(c) damping
(d) ripple suppression
8. If the base current for a transistor operating below saturation is increased,the
collector current
(a) increases and the emitter current decreases
(b) decreases and the emitter current decreases
(c) increases and the emitter current does not change
(d) increases and the emitter current increases
9. For normal operation of a NPN transistor,the base must be
(a) disconnected
(b) negative with respect to the emitter
(c) positive with respect to the emitter
(d) positive with respect to the collector
10. A certain non-inverting amplifier has an Ri of 1 kΩ and an Rf of 100 kΩ, If the
feedback resistor is suddenly removed from the circuit, the voltage gain of the
amplifier
(a) decreases
(b) zero
(c) increases
(d) remains the same
3

21. 11. Which of the following elements of electrical engineering cannot be analyzed
using Ohm’s law?
(a) Capacitors
(b) Inductors
(c) Transistors
(d) Resistance
12. A 2mH, a 3.3mH, and a 0.2mH inductor are connected in series. The total
inductance is
(a) 5.5mH
(b) less than 5.5mH
(c) less than 0.2mH
(d) 55mH
13. Which of the following statements is correct?
(a) Flux is Directly proportional to current
(b) Flux is Inversely proportional to current
(c) Flux is Directly proportional to voltage
(d) None of the above
14. Stator of an alternator consists of
(a) Iron core.
(b) Stator winding.
(c) Both (a) and (b)
(d) None of the above.
15. A resistor is connected across a 50 V source. What is the current in the resistor
if the color code is red, orange, orange, silver?
(a) 21.4 mA
(b) 214 mA
(c) 2 mA
(d) 2.2 mA
4

22. 16. Most widely used motor is
(a) Double cage induction motor
(b) Slip ring induction motor
(c) Squirrel cage induction motor
(d) Synchronous motor
17. What is the maximum possible speed of the transformer in R.P.M?
18. An infinite Bus bar has
(a) Constant voltage
(b) Constant frequency
(c) Constant Current
(d) Both (a) and (b)
19. Determine the type of filter implemented using Op-amp in the given circuit
diagram
First order low-pass filter.
20. Anabhayan uses a single phase induction motor for watering his crops. His
motor is not starting! What could be the issue?
(a) Low quality motor.
(b) Capacitor failure.
(c) Pump air-locked.
(d) Frequency is fluctuating.
5

23. ROUND 2
NAME:
DEPT:
COLLEGE:
1. Sketch the transfer characteristics of figure shown below. Assume the diode is ideal.
2. Find Rf and Ri for figure shown below.

24. 3. Find the resistance between A and B.The resistances are given above the respective
resistors.
4. For the circuit given below, a triangular wave is of 40 Hz is applied to the op-amp.
Predict the output waveform and justify your answer.

25. 5. The figure below is an RLC circuit, The inductor is fully energised, With switch S1 is
open, At t = 0 the S1 is closed, Draw the voltage waveform with respect to time for first
few seconds.
6. Find errors in given boost converter, Redraw the circuit with no errors

26. 7. Rectify the circuit to make, so that it conducts in range of (0-90) alpha
8. Rectify the circuit to make it a working Hartley oscillator.

27. 9. Rectify the circuit to make it a working Full Bridge rectifier.
10. Modify the circuit to get a saw-tooth waveform.

28. 11. Amith is doing an experiment on non-inverting amplifier shown below Given bias volt-
age of +Vcc = +15 V and −Vcc = −15 V , Vi = 1V (Sine wave 40Hz), ACL = 5. Suddenly he
tries to reduce the −Vcc to − 2 V what is the effect on output? Justify your answer.
Your answer here:

29. 12. Correct the circuit to make it integrate the input signal.
13. Adhiyamaan has 7 lamps of 10W each, He was asked to design a circuit where in
lamps are connected in series, But when the supply is given the lamps should turn on
sequentially (one after the other), Help Adhiyamaan to decide what element(s) should
be inserted in the circuit in order to get the desired effect. Draw the circuit.
14. Find the equivalent Capacitance.

30. 15. The given figure shows a domestic electric circuit. Study the below circuit carefully,
and list any 2 errors also justify your answer.
16. Rectify the differentiator circuit shown below.
17. Will the LED glow or Not? Justify your answer too.

31. 18. Find the voltage across 60Ω resistor and justify your answer.
19. Find the time constant of the network given below.

32. 20. Hemachandran is a control engineer. He works at Jhonson lifts Inc. He is asked to
design a control circuit to operate the lift. What type response should his circuit exhibit
for a smooth starting and stopping of the lift at any given floor. Draw the responce
wave Justify.

33. Circuit Debugging Round 2 Answers
Answer 1:
Answer 2:
Rf=0 & Ri= infinity
Answer 3:
3.56 ohms
Answer 4:
Square wave. Due to positive feedback
Answer 5:
Exponentially decaying sine wave
Answer 6:

34. Answer 7:
Answer 8:
Answer 9:

35. Answer 10:
Answer 11:
Negative swinging is clipped to -2 V
Answer 12:
Swap the position of capacitor and resistor
Answer 13:
RL or RC with lamp . like low pass filter
Answer 14:
0.5 micro frarad
Answer 15:
(a) Fuse is incorrectly connected to the neutral wire (N), it
must be connected to the live wire (L).
The fuse wire is always connected in the live wire of the
circuit because if the fuse is put in the neutral wire, then
due to excessive flow of current when the fuse burns,

36. current stops flowing in the circuit, but the appliance
remains connected to the high potential point of the
supply through the live wire.
(b) Bulb B2 is not connected to the neutral wire.
(c) Two switches S1, and S2 in both B1 circuit and no
switch in bulb B2 circuit
Answer 16:
Change to negative feedback
Answer 17:
No , the and gate is grounded
Answer 18:
Zero because shorted
Answer 19:
CR
Answer 20:
First order time response

37. ROUND 3
NAME:
DEPT:
COLLEGE:
1. For the given sine wave in DSO, find the frequency the wave.
2. Using the given UNIVERSAL GATE, build the fundamental AND GATE and
fundamental OR GATE. Also verify their truth tables with the help of the designed
circuit.
3. Design a circuit using IC 741 to amplify a sin wave of f = 1 kHz, to 6 times of the
input signal. Use Vi = 1V . Given R1 = 10 KΩ, and the output should be in-phase with
the input.
4. Build a potential divider circuit using the given resistors to get the output as 4.07 V if
the supply is 15 V .Total resistance of the circuit is 105 kΩ