# Multiple choice question for engineering

## Set 1

1. When a ferromagnetic core is inserted into an inductor, what happens to the flux linkage?

a) Increases

b) Decreases

c) Remains the same

d) Becomes zero

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2. What happens to the current when a ferromagnetic material is introduced within an inductor?

a) Increases

b) Decreases

c) Remains the same

d) Becomes zero

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3. What is the relation between the flux and the magnetizing current when a ferromagnetic core is introduced within the inductor?

a) Directly proportional

b) Inversely proportional

c) Not proportional

d) Current is double of flux

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4. What happens to the effective inductance when a ferromagnetic core is introduced?

a) Increases

b) Decreases

c) Remains the same

d) Becomes zero

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5. A laminated steel ring is wound with 200 turns. When the magnetizing current varies between 5 and 7 A, the magnetic flux varies between 760 and 800 ∫Wb. Calculate the incremental inductance of the coil.

a) 40H

b) 40mH

c) 0.004H

d) 0.004mH

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6. Calculate the number of turns in an inductor with a ferromagnetic core when the inductance is 0.004H, the current changes from 5A to 7A and the flux changes from 760 to 800 ∫Wb.

a) 100

b) 200

c) 300

d) 400

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7. Calculate the change in current in an inductor having inductance 0.004H, number of turns is 200 and the flux changes from 760 to 800 ∫Wb.

a) 2A

b) 4A

c) 6A

d) 8A

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8. Calculate the initial current in an inductor having inductance 0.004H, number of turns is 200 and the flux changes from 760 to 800 ∫Wb. Current changes to 7A.

a) 10A

b) 2A

c) 3A

d) 5A

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9. Calculate the chance in flux of an inductor having inductance 0.004H, number of turns is 200 and the current changes from 5A to 7A.

a) 20 ∫Wb

b) 40∫Wb

c) 60∫Wb

d) 80∫Wb

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10. Calculate the final flux in an inductor having inductance 0.004H, number of turns is 200 and the current changes from 5A to 7A. The initial flux is 760∫Wb.

a) 200∫Wb

b) 400∫Wb

c) 600∫Wb

d) 800∫Wb

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## Set 2

1. 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

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2. What happens to the inductance when the magnetic field strength decreases?

a) Increases

b) Decreases

c) Remains the same

d) Becomes zero

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3. 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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4. 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

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5. 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

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^{-7}*A*N

^{2}/l, hence as the area of cross section A increases, the inductance also increases.

6. What happens to the inductance as the length of the magnetic circuit increases?

a) Increases

b) Decreases

c) Remains the same

d) Becomes zero

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^{-7}*A*N

^{2}/l, hence as the length of the magnetic circuit l increases, the inductance decreases.

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. The unit for inductance is ___________

a) Ohm

b) Henry

c) A/m

d) A/s

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9. 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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10. What is the unit for inductive reactance?

a) Henry

b) Ohm

c) Farad

d) Volts

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## Set 3

1. The energy stored in the capacitor is of _________ nature.

a) Electrostatic

b) Magnetic

c) Neither electrostatic nor magnetic

d) Either electrostatic or magnetic

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2. The energy stored in the inductor is of _________ nature.

a) Electrostatic

b) Magnetic

c) Neither electrostatic nor magnetic

d) Either electrostatic or magnetic

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3. At resonance, the circuit appears __________

a) Inductive

b) Capacitive

c) Either inductive or capacitive

d) Resistive

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4. At resonance, the capacitive energy is ___________ inductive energy.

a) Greater than

b) Less than

c) Equal to

d) Depends on the circuit

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5. At resonance, electrostatic energy is ___________ the magnetic energy.

a) Greater than

b) Less than

c) Equal to

d) Depends on the circuit

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6. The maximum magnetic energy stored in an inductor at any instance is?

a) E=LIm^{2}/2

b) E=LIm/2

c) E=LIm^{2}

d) E=LIm^{2}*2

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^{2}/2, where Im is the maximum current and L is the value of the inductor.

7. The maximum electrostatic energy stored in a capacitor at any instance is?

a) CVm^{2}

b) 1/2*CVm^{2}

c) CVm

d) CVm/2

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^{2}, where C is the capacitance value and Vm is the peak voltage.

8. Q is the ratio of?

a) Active power to reactive power

b) Reactive power to active power

c) Reactive power to average power

d) Reactive power to capacitive power

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9. Find the value of Q if the reactive power is 10W and the average power is 5W.

a) 10

b) 5

c) 2

d) 1

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10. Find the reactive power when the average power is 5W and Q=2.

a) 10W

b) 5W

c) 2W

d) 1W

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## Set 4

1. In an impedance parallel network, the reactive component will ____________ the voltage by 90 degrees.

a) Lead

b) Lag

c) Either lead or lag

d) Depends on the circuit

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2. In an impedance parallel network the reactive component will either lead or lag the voltage by _________ degrees.

a) 0

b) 90

c) 45

d) 180

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3. In an impedance parallel network the reactive component will either lead or lag the ________ by 90 degrees.

a) Voltage

b) Current

c) Either voltage or current

d) Cannot be determined

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4. The reactive component in an impedance parallel circuit leads the voltage when the current _________ the voltage.

a) Leads

b) Lags

c) Either leads or lags

d) Cannot be determined

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5. The active component in an impedance parallel circuit will __________ the voltage.

a) Leads

b) Lags

c) Be in phase with

d) Either leads or lags

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6. The phase difference between the active component of an impedance parallel circuit and the voltage in the network is __________

a) 0

b) 90

c) 180

d) 360

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7. The quadrature component is also known as?

a) Active component

b) Reactive component

c) Either active or reactive component

d) Neither active nor reactive component

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8. What is the phase relation between IL and V from the following circuit?

a) IL lags V

b) IL leads V

c) IL and V are in phase

d) No relation

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9. What is the expression for the current in the inductor from the following circuit?

a) V/I

b) V/XL

c) 0

d) Cannot be determined

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10. Find the total current if IL=2A and Ir=8A.

a) 3A

b) -3A

c) 7A

d) 10A

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## Set 5

1. If two bulbs are connected in parallel and one bulb blows out, what happens to the other bulb?

a) The other bulb blows out as well

b) The other bulb continues to glow with the same brightness

c) The other bulb glows with increased brightness

d) The other bulb stops glowing

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2. Calculate the current across the 20 ohm resistor.

a) 10A

b) 20A

c) 6.67A

d) 36.67A

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3. In a parallel circuit, with a number of resistors, the voltage across each resistor is ________

a) The same for all resistors

b) Is divided equally among all resistors

c) Is divided proportionally across all resistors

d) Is zero for all resistors

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4. The current in each branch of a parallel circuit is proportional to_______

a) The amount of time the circuit is on for

b) Proportional to the value of the resistors

c) Equal in all branches

d) Proportional to the power in the circuit

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5. Calculate the total current in the circuit.

a) 20A

b) 10A

c) 12A

d) 15A

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6. The voltage across the open circuit is?

a) 100V

b) Infinity

c) 90V

d) 0V

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7. The voltage across the short is?

a) 135V

b) Infinity

c) Zero

d) 11.25V

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8. If the current in the circuit=5A, find the value of x.

a) 27 ohm

b) 5 ohm

c) 12 ohm

d) 135 ohm

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9. The currents in the three branches of a parallel circuit are 3A, 4A and 5A. What is the current leaving it?

a) 0A

b) Insufficient data provided

c) The largest one among the three values

d) 12A

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10. The total resistance between A and B are?

a) 20 ohm

b) 5 ohm

c) 80 ohm

d) 0 ohm