# Multiple choice question for engineering

## Set 1

1. An 8microF capacitor is connected in series with a 0.5 megaohm resistor. The DC voltage supply is 200V. Calculate the time constant.

a) 1s

b) 2s

c) 3s

d) 4s

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^{-6}*4*10

^{6}=4s.

2. An 8microF capacitor is connected in series with a 0.5 megaohm resistor. The DC voltage supply is 200V. Calculate the initial charging current.

a) 100 microA

b) 500 microA

c) 400 microA

d) 1000microA

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^{6s})= 400*10

^{-6}A= 400 microA.

3. An 8microF capacitor is connected in series with a 0.5 megaohm resistor. The DC voltage supply is 200V. Calculate the time taken for the potential difference across the capacitor to gow to 160V.

a) 6.44s

b) 7.77s

c) 2.33s

d) 3.22s

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^{-t}/RC), we get t=6.44s.

4. An 8microF capacitor is connected in series with a 0.5 megaohm resistor. The DC voltage supply is 200V. Calculate the voltage in the capacitor 4s after the power is supplied.

a) 123.4V

b) 126.4V

c) 124.5V

d) 132.5V

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^{-t}/RC). Substituting the values in the given equation, we get Vc= 126.4V.

5. An 8microF capacitor is connected in series with a 0.5 megaohm resistor. The DC voltage supply is 200V. Calculate the current in the capacitor 4s after the power is supplied.

a) 150 microA

b) 149 microA

c) 148 microA

d) 147 microA

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6. The discharging time constant of a circuit consisting of a capacitor is the time taken for the charge in the capacitor to become __________% of the initial charge.

a) 33

b) 63

c) 37

d) 36

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^{-t}/RC). When RC=t, we have: Q=Q0(e

^{-1})= 0.37*Q0. Hence the time constant is the time taken for the charge in a capacitive circuit to become 0.37 times its initial charge.

7. The discharging time constant of a circuit consisting of a capacitor is the time taken for the charge in the capacitor to become __________% of the initial charge.

a) 33

b) 63

c) 37

d) 36

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^{-t}/RC). When RC=t, we have: Q=Q0(e

^{-1})= 0.37*Q0. Hence the time constant is the time taken for the charge in a capacitive circuit to become 0.37 times its initial charge.

8. A circuit has a resistance of 2 ohm connected in series with a capacitance of 6F. Calculate the discharging time constant.

a) 3

b) 1

c) 12

d) 8

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9. What is the value of current in a discharging capacitive circuit if the initial current is 2A at time t=RC.

a) 0.74A

b) 1.26A

c) 3.67A

d) 2.89A

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10. While discharging, what happens to the current in the capacitive circuit?

a) Decreases linearly

b) Increases linearly

c) Decreases exponentially

d) Increases exponentially

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## Set 2

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

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2. Among the following, which is the right formula for inductance?

a) L=NΦ/t

b) L=NΦt

c) L=N/Φt

d) L=NΦ^{2}t

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3. For a coil having a magnetic circuit of constant reluctance, the flux is ___________ to the current.

a) Directly proportional

b) Inversely proportional

c) Not related

d) Very large compared to

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4. For a coil having a magnetic circuit of constant reluctance, if the flux increases, what happens to the current?

a) Increases

b) Decreases

c) Remains constant

d) Becomes zero

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5. The unit for inductance is ___________

a) Ohm

b) Henry

c) A/m

d) A/s

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6. If either the inductance or the rate of change of current is doubled, the induced e.m.f?

a) Remains constant

b) Becomes zero

c) Doubles

d) Becomes half

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7. If the current changes from 5A to 3A in 2 seconds and the inductance is 10H, calculate the emf.

a) 5V

b) 10V

c) 15V

d) 20V

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8. If the current changes from 5A to 3A in x sec and inductance is 10H. The emf is 10V, calculate the value of x.

a) 2s

b) 3s

c) 4s

d) 5s

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9. If the current changes from 3A to 5A in 2s and the emf is 10V. Calculate the inductance.

a) 10H

b) 20H

c) 30H

d) 40H

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10. If the current changes from 20A to 10A in 5 seconds and the value of inductance is 1H, calculate the emf induced.

a) 8V

b) 6V

c) 4V

d) 2V

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## Set 3

1. Inductor does not allow sudden changes in?

a) Voltage

b) Current

c) Resistance

d) Inductance

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2. 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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3. If the resistance in a circuit is 2 ohm and the inductive resistance is 20 ohm, calculate the power factor.

a) 10

b) 20

c) 30

d) 40

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4. If the power factor is 10 and the resistance is 2 ohm, calculate the inductive reactance.

a) 10 ohm

b) 20 ohm

c) 30 ohm

d) 40 ohm

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5. An induced emf is said to be ___________

a) Inductive

b) Capacitive

c) Resistive

d) Cannot be determined

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6. In a pure inductive circuit, the power factor is?

a) Maximum

b) Minimum

c) 0

d) Infinity

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7. 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

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8. Among the following, which is the right formula for inductance?

a) L=NΦ/t

b) L=NΦt

c) L=N/Φt

d) L=NΦ^{2t}

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9. If the current in a coil having a constant inductance of L henrys grows at a uniform rate, what is the value of the average current?

a) I

b) I/2

c) I/4

d) 0

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10. Find the average current in an inductor if the total current in the inductor is 30A.

a) 10A

b) 26A

c) 15A

d) 5A

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## Set 4

1. In case of Inductive circuit, Frequency is ______________ to the inductance.

a) Directly proportional

b) Inversely proportional

c) Unrelated

d) Much greater than

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2. If the current and voltage are 90 degree out of phase, the power factor will be?

a) 0

b) Infinity

c) 1

d) Insufficient information provided

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3. If the power factor is 10 and the value of inductive reactance is 20 ohm, calculate the resistance in the circuit.

a) 1 ohm

b) 2 ohm

c) 3 ohm

d) 4 ohm

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4. What is the unit for inductive reactance?

a) Henry

b) Ohm

c) Farad

d) Volts

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5. If the current in a coil having a constant inductance of L henrys grows at a uniform rate, what is the value of the average current?

a) I

b) I/2

c) I/4

d) 0

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6. Find the average current in an inductor if the total current in the inductor is 26A.

a) 10A

b) 26A

c) 13A

d) 5A

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7. Calculate the emf induced in an inductor if the inductance is 10H and the current is 2A in 4s.

a) 2.5V

b) 1.5V

c) 3.5V

d) 5V

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8. Calculate the current in an inductor if the energy stored is 160J and the inductance is 20H.

a) 1A

b) 2A

c) 3A

d) 4A

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^{2}/2t Substituting the values from the given question, we get I=4A.

9. Find the time taken for the current in an inductor to change to 2A from 0A if the power in the inductor is 5W. The value of inductance is 10H.

a) 1s

b) 2s

c) 3s

d) 4s

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^{2}/2 Substituting the values from the given question, we get t=4s.

10. An induced emf is said to be?

a) Inductive

b) Capacitive

c) Resistive

d) Cannot be determined

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## Set 5

1. The instantaneous voltage is a product of the resistance and the _____________ current in a resistive circuit.

a) Instantaneous

b) Average

c) RMS

d) Peak

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2. Find the value of the instantaneous voltage if the resistance is 2 ohm and the instantaneous current in the circuit is 5A.

a) 5V

b) 2V

c) 10V

d) 2.5V

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3. The power for a purely resistive circuit is zero when?

a) Current is zero

b) Voltage is zero

c) Both current and voltage are zero

d) Either current or voltage is zero

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4. If the maximum voltage in the circuit is 10V and the resistance is 5 ohm, calculate the maximum current in the circuit.

a) 1A

b) 2A

c) 3A

d) 4A

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5. Calculate the resistance in the circuit if the rms voltage is 20V and the rms current is 2A.

a) 2 ohm

b) 5 ohm

c) 10 ohm

d) 20 ohm

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6. The correct expression for the instantaneous current in a resistive circuit is?

a) i=Vm(sint)/R

b) i=Vm(cost)/R

c) i=V(sint)/R

d) i=V(cost)/R

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7. Can ohm’s law be applied in an ac circuit?

a) Yes

b) No

c) Depends on the rms current

d) Depends on the rms voltage

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8. 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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9. What is the effective value of current?

a) RMS current

b) Average current

c) Instantaneous current

d) Total current

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10. 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