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# Multiple choice question for engineering

## Set 1

1. An RL network is one which consists of ____________
a) Resistor and capacitor in parallel
b) Resistor and capacitor in series
c) Resistor and inductor in parallel
d) Resistor and inductor in series

Answer: d [Reason:] An R-L network is a network which consists of a resistor which is connected in series to an inductor.

2. At DC, inductor acts as _____________
a) Open circuit
b) Short circuit
c) Resistor
d) Inductor

Answer: b [Reason:] At DC, the inductor acts as short circuit because the inductive resistance is zero. The frequency of a DC circuit is 0. The inductive resistance=(2*pi*f*L). Therefore, if the frequency is 0, the inductive resistance is zero and it acts as an short circuit.

3. In an RL series circuit, when the switch is closed and the circuit is complete, what is the response?
a) Response does not vary with time
b) Decays with time
c) Increases with time
d) First increases, then decreases

Answer: b [Reason:] In an RL series circuit, the response decays with time because according to the equation, there is an exponential decrease in the response.

4. If the switch is closes at t=0, what is the current in the circuit? a) 0A
b) 10A
c) 20A
d) 30A

Answer: a [Reason:] Initially, when the switch is open, the current in the circuit is 0. As soon as the switch is closes at t=0+, the inductor acts as an open circuit, hence the current in the circuit is zero.

5. What is the voltage across the inductor at t=0? a) 0V
b) 20V
c) 60V
d) 58V

Answer: c [Reason:] Initially, when the switch is open, the current in the circuit is 0. As soon as the switch is closes at t=0+, the inductor acts as an open circuit, hence the current in the circuit is zero. Since the current in the circuit is zero, there is no voltage drop across the resistor and the voltage across the inductor is equal to the supply voltage, which is equal to 60V.

6. What is the expression for current in the given circuit? a) i=2(e-2t)A
b) i=2(1-e-2t)A
c) i=2(e2t)A
d) i=2(1+e-2t)A

Answer: b [Reason:] At t = 0+ the current in the circuit is zero. Therefore at t = 0+, i = 0, 0 = c + 2, c = -2. Substituting the value of c in the current equation, we have i = 2(1-e-2t)A.

7. At steady state, inductor acts as ____________
a) Open circuit
b) Short circuit
c) Resistor
d) Capacitor

Answer: b [Reason:] At steady state, inductor acts as a short circuit because at steady state maximum current flows across the inductor. Hence it acts as a zero resistance source or an open circuit.

8. At steady state, the current in the inductor is?
a) Maximum
b) Minimum
c) Zero
d) Infinity

Answer: a [Reason:] At steady state maximum current flows in the inductor because it acts as an open circuit.

9. Initially, when the switch in a series RL circuit is closed, the inductor acts as?
a) Open circuit
b) Short circuit
c) Resistor
d) Capacitor

Answer: a [Reason:] Initially, when the switch in a series RL circuit is closed, the inductor acts as an open circuit. This is because the current gradually increases as the time increases. At t=0, the current in the inductor is zero, hence it acts as an open circuit.

10. Initially, when the switch in a series RL circuit is closed, the current in the inductor is?
a) Maximum
b) Minimum
c) Zero
d) Infinity

Answer: c [Reason:] Initially, when the switch in a series RL circuit is closed, the inductor acts as an open circuit. Current in an open circuit is zero, hence the inductor current is zero.

## Set 2

1. Paper capacitor is a type of _________
a) Fixed capacitor
b) Variable capacitor
c) Either fixed or variable depending on its usage
d) Neither fixed nor variable

Answer: a [Reason:] Paper capacitors are fixed capacitors because, like fixed capacitors, its capacitance value remains constant. In paper capacitors, paper is used as the dielectric.

2. A capacitor using chemical reactions to store charge are _______
a) Paper capacitor
b) Ceramic capacitor
c) Polyester capacitor
d) Electrolyte capacitor

Answer: d [Reason:] Electrolyte capacitors use chemical processes like pyrolysis to store charge between its plates.

3. Which, among the following, is the odd one out?
a) Ceramic capacitor
b) Electrolyte capacitor
c) Tuning capacitor
d) Paper capacitor

Answer: c [Reason:] All, ceramic capacitor, electrolyte capacitor and paper capacitor, are fixed capacitors whereas tuning capacitors are variable capacitor, hence it is the odd one out.

4. In a variable capacitor, capacitance can be varied by ______
a) Turning the rotatable plates in or out
b) Sliding the rotatable plates
c) Changing the plates
d) Changing the material of plates

Answer: a [Reason:] As the plates are rotated, the area of the plates between which the field is, will vary. Capacitance depends on area, hence as area varies, capacitance also varies.

5. The simplest kind of capacitor is ________
a) Ceramic capacitor
b) Electrolyte capacitor
c) Tuning capacitor
d) Paper capacitor

Answer: d [Reason:] The paper capacitor consists of two strips of aluminium foil separated by sheets of waxed paper. This whole setup is rolled up into the form of a cylinder. Since the materials requires for its construction are easily available, it is the simplest kind of capacitor.

6. Capacitor preferred when there is high frequency in the circuits is _______
a) Electrolyte capacitor
b) Mica capacitor
c) Air capacitor
d) Glass capacitor

Answer: b [Reason:] Mica capacitors are preferred for high frequency circuits because they have low ohmic losses and less reactance.

7. The type of capacitors used in communication transmitters are?
a) Electrolyte capacitor
b) Variable capacitor
c) Air capacitor
d) Glass capacitor

Answer: b [Reason:] The variable capacitor is used to change the resonant frequency for fine modification to the communication transmitter.

8. Which capacitors relatively costly?
a) Electrolyte capacitor
b) Mica capacitor
c) Air capacitor
d) Glass capacitor

Answer: b [Reason:] Mica capacitors are relatively expensive because it consists either of alternate layers of mica and metal foil clamped tightly together, or of thin films of silver on the two sides of a mica sheet. Silver is an expensive metal, hence mica capacitors are expensive.

9. ____________ capacitors usually have a colour code to find its value.
a) Electrolyte capacitor
b) Variable capacitor
c) Polyester capacitor
d) Glass capacitor

Answer: c [Reason:] Polyester capacitors usually come with a colour code because they are very small and their values cannot be printed on its body.

10. ______________ capacitors have a high leakage voltage.
a) Electrolyte capacitor
b) Variable capacitor
c) Air capacitor
d) Polyester capacitor

Answer: d [Reason:] Polyester capacitors can operate at high voltages, that is, a few thousand volts, and the leakage resistance is high, that is, usually 100 M.

## Set 3

1. Among the following, which is the right formula for inductance?
a) L=emf*t/I
b) L=emf/t*I
c) L=emf*I/t
d) L=emf*t*I

Answer: a [Reason:] The average emf induced is proportional to the current per unit time, the constant of proportionality being L. Hence emf=LI/t. Making L the subject of the formula, we get: L=emf*t/I.

2. Among the following, which is the right formula for inductance?
a) L=NΦ/t
b) L=NΦt
c) L=N/Φt
d) L=NΦ2t

Answer: a [Reason:] The average emf induced in a coil= L=NΦ/t.

3. The unit for inductance is ___________
a) Ohm
b) Henry
c) A/m
d) A/s

Answer: b [Reason:] The unit of induction is named after a famous scientist Joseph Henry who independently discovered electromagnetic induction.

4. What happens to the inductance when the magnetic field strength decreases?
a) Increases
b) Decreases
c) Remains the same
d) Becomes zero

Answer: b [Reason:] Inductance is directly proportional to the magnetic field strength in the coil, hence as the magnetic field strength increases, inductance decreases.

5. As the number of turns in the coil increases, what happens to the inductance of the coil?
a) Increases
b) Decreases
c) Remains the same
d) Becomes zero

Answer: a [Reason:] Inductance is directly proportional to the square of the number of turns in the coil, hence as the number of turns increases, inductance also increases.

6. What is the unit for inductive reactance?
a) Henry
b) Ohm
d) Volts

Answer: b [Reason:] Inductive reactance is nothing but the impedance. Impedance is the AC equivalent of resistance, hence the unit for inductive reactance is ohm.

7. What happens to the inductance as the length of the magnetic circuit increases?
a) Increases
b) Decreases
c) Remains the same
d) Becomes zero

Answer: b [Reason:] The formula for inductance is: L=4*pi*10-7*A*N2/l, hence as the length of the magnetic circuit l increases, the inductance decreases.

8. The types of inductors are ____________
a) Fixed and variable
b) Only fixed
c) Only variable
d) Neither fixed nor variable

Answer: a [Reason:] The two types of inductors are fixed and variable inductors. Fixed inductors are those whose inductance value cannot be changed. Variable inductors are those whose values can be changed as and when required.

9. What happens to the inductance as the area of cross section of the coil increases?
a) Increases
b) Decreases
c) Remains the same
d) Becomes zero

Answer: a [Reason:] The formula for inductance is: L=4*pi*10-7*A*N2/l, hence as the area of cross section A increases, the inductance also increases.

10. When the coil is wrapped around a ferromagnetic core, why is it difficult to determine the inductance?
a) The variation of flux is no longer proportional to the variation of current
b) Current does not exist in the coil
c) Flux does not exist in the coil
d) The value of current is too large to measure

Answer: a [Reason:] When a coil is wrapped around a ferromagnetic core, it is difficult to determine the inductance because the variation of flux is no longer proportional to the variation of current.

## Set 4

1. In a series RLC circuit, the phase difference between the voltage across the capacitor and the voltage across the resistor is?
a) 0 degrees
b) 90 degrees
c) 180 degrees
d) 360 degrees

Answer: b [Reason:] In a series RLC circuit, the phase difference between the voltage across the capacitor and the voltage across the resistor is 90 degrees.

2. In a series RLC circuit, the phase difference between the voltage across the inductor and the voltage across the resistor is?
a) 0 degrees
b) 90 degrees
c) 180 degrees
d) 360 degrees

Answer: b [Reason:] In a series RLC circuit, the phase difference between the voltage across the inductor and the voltage across the resistor is 90 degrees.

3. In a series RLC circuit, the phase difference between the voltage across the capacitor and the voltage across the inductor is?
a) 0 degrees
b) 90 degrees
c) 180 degrees
d) 360 degrees

Answer: c [Reason:] In a series RLC circuit, the phase difference between the voltage across the capacitor and the voltage across the inductor is 180 degrees.

4. In a series RLC circuit, the phase difference between the voltage across the resistor and the current in the circuit is?
a) 0 degrees
b) 90 degrees
c) 180 degrees
d) 360 degrees

Answer: a [Reason:] In a series RLC circuit, the phase difference between the voltage across the resistor and the current in the circuit is 0 degrees because they are in phase.

5. In a series RLC circuit, the phase difference between the voltage across the capacitor and the current in the circuit is?
a) 0 degrees
b) 90 degrees
c) 180 degrees
d) 360 degrees

Answer: b [Reason:] In a series RLC circuit, the phase difference between the voltage across the capacitor and the current in the circuit is 90 degrees.

6. In a series RLC circuit, the phase difference between the voltage across the inductor and the current in the circuit is?
a) 0 degrees
b) 90 degrees
c) 180 degrees
d) 360 degrees

Answer: b [Reason:] In a series RLC circuit, the phase difference between the voltage across the inductor and the current in the circuit is 90 degrees.

7. The current in the inductor lags the voltage in a series RLC circuit ___________ resonant frequency.
a) Above
b) Below
c) Equal to
d) Depends on the circuit

Answer: a [Reason:] The current in the inductor lags the voltage in a series RLC circuit above the resonant frequency.

8. The current in the capacitor leads the voltage in a series RLC circuit ___________ resonant frequency.
a) Above
b) Below
c) Equal to
d) Depends on the circuit

Answer: b [Reason:] The current in the capacitor leads the voltage in a series RLC circuit below the resonant frequency.

9. The current in the inductor ___________ the voltage in a series RLC circuit above the resonant frequency.
b) Lags
c) Equal to
d) Depends on the circuit

Answer: a [Reason:] The current in the inductor lags the voltage in a series RLC circuit above the resonant frequency.

10. The current in the capacitor ___________ the voltage in a series RLC circuit below the resonant frequency.
b) Lags
c) Equal to
d) Depends on the circuit

Answer: b [Reason:] The current in the capacitor leads the voltage in a series RLC circuit above the resonant frequency.

## Set 5

1. The variation of a quantity such as voltage or current shown on a graph is known as ___________
a) Waveform
b) Peak value
b) Instantaneous value
d) Period

Answer: a [Reason:] The variation of a quantity, which is voltage or current in this case, shown on a graph with the x-axis as time is known as waveform.

2. What is the duration of one cycle known as _________
a) Waveform
b) Peak value
b) Instantaneous value
d) Period

Answer: d [Reason:] The duration of one cycle is known as a period. A function which repeats the same waveform at equal intervals of time is known as a periodic function.

3. The repetition of a variable quantity, recurring at equal intervals, is known as ___________
a) Waveform
b) Instantaneous value
c) Cycle
d) Period

Answer: c [Reason:] Each repetition of a variable quantity, recurring at equal intervals, is termed as a cycle.

4. The value of a given waveform at any instant time is termed as ___________
a) Waveform
b) Instantaneous value
c) Cycle
d) Period

Answer: b [Reason:] Instantaneous value is the value of the waveform at that instant. Hence the value of a given waveform at any instant time is termed as instantaneous value.

5. The maximum instantaneous value measured from zero value is known as?
a) Peak value
b) Peak to peak value
c) Cycle
d) Period

Answer: a [Reason:] The maximum instantaneous value measured from the zero value is termed as the peak value.

6. The maximum variation between the maximum positive and the maximum negative value is known as?
a) Peak value
b) Peak to peak value
c) Cycle
d) Period

Answer: a [Reason:] The maximum variation between the maximum positive instantaneous value and the maximum negative instantaneous value is the peak-to-peak value.

7. What is the correct reaction between peak value and peak to peak value for a sinusoidal waveform?
a) Vp=4Vp-p
b) Vp=Vp-p
c) Vp-p=2Vp
d) Vp=2Vp-p

Answer: c [Reason:] The maximum variation between the maximum positive instantaneous value and the maximum negative instantaneous value is the peak-to-peak value. For a sinusoidal waveform, it is twice the peak value. Hence Vp-p=2Vp.

8. If the peak to peak voltage is 10V, calculate the peak voltage.
a) 10V
b) 2V
c) 4V
d) 5V

Answer: d [Reason:] Vp-p=2Vp Substituting the values from the question, we get Vp=5V.

9. If the peak voltage is 9V, calculate the peak to peak voltage.
a) 9V
b) 20V
c) 18V
d) 12V