# Multiple choice question for engineering

## Set 1

1. Find the total voltage applied in a series RLC circuit when i=3mA, VL=30V, VC=18V and R=1000 ohms.

a) 3.95V

b) 51V

c) 32.67V

d) 6.67V

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^{-3}=3V. Therefore, total voltage= 30+18+3=51V.

2. In an RLC circuit, which of the following is always used as a vector reference?

a) Voltage

b) Resistance

c) Impedance

d) Current

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3. In an RLC circuit, the power factor is always ____________

a) Positive

b) Negative

c) Depends on the circuit

d) Zero

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4. In an RLC series phasor, we start drawing the phasor from which quantity?

a) Voltage

b) Resistance

c) Impedance

d) Current

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5. What is the correct expression for the phase angle in an RLC series circuit?

a) φ=tan^{-1}(XL-XC)/R

b) φ=tan^{-1} (XL+XC)/R

c) φ=tan(XL-XC)/R

d) φ=tan^{-1} (XL-XC)

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^{-1}(XL-XC)/R.

6. When is tanφ positive?

a) When inductive reactance is less than capacitive reactance

b) When inductive reactance is greater than capacitive reactance

c) When inductive reactance is equal to capacitive reactance

d) When inductive reactance is zero

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7. When is tanφ negative?

a) When inductive reactance is less than capacitive reactance

b) When inductive reactance is greater than capacitive reactance

c) When inductive reactance is equal to capacitive reactance

d) When inductive reactance is zero

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8. When is current in phase with the voltage?

a) When XL>XC

b) When XL<XC

c) When XL=XC

d) When XC=infinity

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9. What is resonance condition?

a) When XL>XC

b) When XL<XC

c) When XL=XC

d) When XC=infinity

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10. What is the frequency in resonance condition?

a) Minimum

b) Maximum

c) Cannot be determined

d) Zero

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## Set 2

1. What is the time constant of an inductive circuit?

a) LR

b) R/L

c) 1/LR

d) L/R

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2. Among the following, which is the right formula for decay in an inductive circuit?

a) i=I(1-e^{-t}/time constant)

b) i=I(1-e^{t} /time constant)

c) i=(1-e^{-t} /time constant)

d) i=I(e^{-t} /time constant)

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3. The discharging time constant of a circuit consisting of an inductor is the time taken for the voltage in the inductor to become __________% of the initial voltage.

a) 33

b) 63

c) 37

d) 36

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^{-t}/time constant). When time constant=t, we have: V=V0(e

^{-1})= 0.36*V0. Hence the time constant is the time taken for the charge in an inductive circuit to become 0.36 times its initial charge.

4. A coil has a resistance of 4 ohm and an inductance of 2H. Calculate its time constant.

a) 1s

b) 2s

c) 0.5s

d) 5s

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5. In case of Inductive circuit, Frequency is ______________ to the current.

a) Directly proportional

b) Inversely proportional

c) Unrelated

d) Much greater than

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6. Calculate the time constant of an inductive circuit having resistance 5 ohm and inductance 10H.

a) 2s

b) 4s

c) 5s

d)10s

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7. Calculate the inductance in an inductive circuit whose time constant is 2 and the resistance is 5 ohm.

a) 10H

b) 20H

c) 5H

d) 15H

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8. A coil has a resistance of 4 ohm and an inductance of 2H. It is connected to a 20V dc supply. Calculate the final value of current in the circuit.

a) 5A

b) 10A

c) 15A

d) 20A

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9. What happens to the inductance when the current in the coil becomes double its original value?

a) Becomes half

b) Becomes four times

c) Becomes infinity

d) Becomes double

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10. What is the total applied voltage in an inductive circuit?

a) V=Ri+Ldi/dt

b) V=Ri+di/dt

c) V=i+Ldi/dt

d) V=R+Ldi/dt

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## Set 3

1. What is the total applied voltage in an inductive circuit?

a) V=Ri+Ldi/dt

b) V=Ri+di/dt

c) V=i+Ldi/dt

d) V=R+Ldi/dt

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2. What is Helmholtz equation?

a) i=I(1-e^{Rt/L})

b) i=I(1-e^{-Rt/L})

c) i=I(1+e^{-Rt/L})

d) i=I(e^{-Rt/L})

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^{-Rt/L}).

3. Among the following, which is the right formula for growth in an inductive circuit?

a) VL=V(1-e^{-t}/time constant)

b) VL=V(1-e^{t} /time constant)

c) VL=(1-e^{-t} /time constant)

d) VL=V(e^{-t} /time constant)

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^{-t}/time constant). As the time increases, the current in the inductor increases hence the voltage also increases.

4. The charging time constant of a circuit consisting of an inductor is the time taken for the voltage in the inductor to become __________% of the initial voltage.

a) 33

b) 63

c) 37

d) 36

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^{-1})= 0.63*V0. Hence the time constant is the time taken for the charge in an inductive circuit to become 0.63 times its initial charge.

5. What is the time constant of an inductive circuit?

a) LR

b) R/L

c) 1/LR

d) L/R

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6. A coil has a resistance of 4 ohm and an inductance of 2H. Calculate its time constant.

a) 1s

b) 2s

c) 0.5s

d) 5s

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7. A coil has a resistance of 4 ohm and an inductance of 2H. It is connected to a 20V dc supply. Calculate the final value of current in the circuit.

a) 5A

b) 10A

c) 15A

d) 20A

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8. A coil has a resistance of 4 ohm and an inductance of 2H. It is connected to a 20V dc supply. Calculate the value of current 1s after the switch is closed.

a) 5.44A

b) 4.32A

c) 6.56A

d) 2.34A

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^{Rt/L}) I=V/R=5A Substituting the remaining values from the given question, we get i=4.32A.

9. What happens to the inductance when the current in the coil becomes double its original value?

a) Becomes half

b) Becomes four times

c) Becomes infinity

d) Becomes double

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10. Calculate the inductance in an inductive circuit whose time constant is 2s and the resistance is 5 ohm.

a) 10H

b) 20H

c) 5H

d) 15H

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## Set 4

1. Ammeters and voltmeters are calibrated to read?

a) RMS value

b) Peak value

c) Average value

d) Instantaneous value

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2. The rms value is _________ times he maximum value

a) 1.414

b) 0.5

c) 2

d) 0.707

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3. The rms value is 0.707 times the _________ value.

a) Peak

b) Instantaneous

c) Average

d) DC

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4. If the phasors are drawn to represent the rms values, instead of the maximum values, what would happen to the phase angle between quantities?

a) Increases

b) Decreases

c) Remains constant

d) Becomes zero

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5. Usually phasor diagrams are drawn representing?

a) RMS value

b) Peak value

c) Average value

d) Instantaneous value

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6. A phasor has frozen at 30 degrees, find the value of the phase angle?

a) 30 degrees

b) 60 degrees

c) 120 degrees

d) 180 degrees

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7. The time axis of an AC phasor represents?

a) Time

b) Phase angle

c) Voltage

d) Current

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8. The length of the phasor represents?

a) Magnitude of the quantity

b) Direction of the quantity

c) Neither magnitude nor direction

d) Either magnitude or direction

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9. What is the type of current obtained by finding the square of the currents and then finding their average and then fining the square root?

a) RMS current

b) Average current

c) Instantaneous current

d) Total current

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10. For a direct current, the rms current is ________ the mean current.

a) Greater than

b) Less than

c) Equal to

d) Not related to

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## Set 5

1. Find the average value of current when the current that are equidistant are 4A, 5A and 6A.

a) 5A

b) 6A

c) 15A

d) 10A

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2. What is the current found by finding the current in n equidistant regions and dividing by n?

a) RMS current

b) Average current

c) Instantaneous current

d) Total current

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3. RMS stands for ________

a) Root Mean Square

b) Root Mean Sum

c) Root Maximum sum

d) Root Minimum Sum

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4. What is the type of current obtained by finding the square of the currents and then finding their average and then fining the square root?

a) RMS current

b) Average current

c) Instantaneous current

d) Total current

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5. __________ current is found by dividing the area enclosed by the half cycle by the length of the base of the half cycle.

a) RMS current

b) Average current

c) Instantaneous current

d) Total current

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6. What is the effective value of current?

a) RMS current

b) Average current

c) Instantaneous current

d) Total current

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7. In a sinusoidal wave, average current is always _______ rms current.

a) Greater than

b) Less than

c) Equal to

d) Not related

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8. For a rectangular wave, average current is ______ rms current.

a) Greater than

b) Less than

c) Equal to

d) Not related

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9. Peak value divided by the rms value gives us?

a) Peak factor

b) Crest factor

c) Both peak and crest factor

d) Neither peak nor crest factor

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10. Calculate the crest factor if the peak value of current is 10A and the rms value is 2A.

a) 5

b) 10

c) 5A

d) 10A