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Multiple choice question for engineering

Set 1

1. What is a current transformer?
a) transformer used with an A.C. ammeter
b) transformer used with an D.C. ammeter
c) transformer used with an A.C. voltmeter
d) transformer used with an D.C. voltmeter

View Answer

Answer: a [Reason:] A transformer used to extend the range of an A.C. ammeter is known as a current transformer. A current transformer is also abbreviated as C.T.

2. What is a potential transformer?
a) transformer used with an D.C. ammeter
b) transformer used with an A.C. voltmeter
c) transformer used with an D.C. ammeter
d) transformer used with an A.C. voltmeter

View Answer

Answer: b [Reason:] A transformer used to extend the range of an A.C. voltmeter is known as a potential transformer. A potential transformer is also abbreviated as P.T.

3. C.T. and P.T. are used for _________
a) measuring low current and voltages
b) measuring very low current and voltages
c) measuring high currentsand voltages
d) measuring intermediate currents and voltages

View Answer

Answer: c [Reason:] C.T. is basically used for the measurement of high currents. A P.T. is usually used for the measurement of high voltages. They are used with A.C. ammeters and voltmeters in order to extend their range.

4. The primary winding of a C.T. has _________
a) a larger number of turns
b) no turns at all
c) intermediate number of turns
d) a few turns

View Answer

Answer: d [Reason:] The primary winding of a C.T. has a very few number of turns. It is connected in series with the load circuit through which the primary current flows.

5. The secondary winding of a C.T. has _________
a) a large number of turns
b) a few turns
c) no turns at all
d) intermediate number of turns

View Answer

Answer: a [Reason:] Secondary winding of a C.T. has a large number of turns. It is connected in series to an ammeter through which a small portion of the current flows through.

6. Turns ration for a C.T. is _________
a) n = NpNs
b) n = NsNp
c) n = 1Np
d) n = Ns

View Answer

Answer: b [Reason:] The turns ratio for a C.T. is defined as the ratio of the number of turns in the secondary to the number of turns in the primary. It is given by the relation n = NsNp

7. The primary winding of a P.T. has _________
a) intermediate number of turns
b) no turns at all
c) a larger number of turns
d) a few turns

View Answer

Answer: c [Reason:] The primary winding of a P.T. has a very large number of turns. It is connected in parallel with the load whose voltage is to be measured.

8. The secondary winding of a P.T. has _________
a) a large number of turns
b) intermediate number of turns
c) no turns at all
d) a few turns

View Answer

Answer: d [Reason:] Secondary winding of a P.T. has a few number of turns. A low range voltmeter is connected in parallel with the secondary winding.

9. Turns ration for a C.T. is _________
a) n = NpNs
b) n = NsNp
c) n = 1Np
d) n = Ns

View Answer

Answer: a [Reason:] The turns ratio for a P.T. is defined as the ratio of the number of turns in the primary to the number of turns in the secondary. It is given by the relation n = NpNs.

Set 2

1. A bridge circuit is used for the measurement of the following components:
a) Resistance, capacitance and inductance
b) Diode, triode and thyristor
c) Transistor, thermistor and antenna
d) LED, op amp and transducer

View Answer

Answer: a [Reason:] A bridge circuit is basically used for the measurement of basic electronic components such as resistance, capacitance and inductance.

2. A simple bridge circuit consists of a network of __________
a) 3 resistance arms
b) 2 resistance arms
c) 4 resistance arms
d) 6 resistance arms

View Answer

Answer: c [Reason:] A simple bridge circuit is made of a network consisting of 4 resistance arms. Usually a galvanometer is connected between the ends of the opposite two junctions in order to measure the flow of current.

3. What is applied to the two opposite junctions of a bridge circuit.
a) source of voltage
b) source of current
c) source of power
d) source of impedance

View Answer

Answer: b [Reason:] A current source is connected between the two opposite junctions of a bridge circuit. Deflection of the galvanometer in the circuit indicates the flow of current.

4. A bridge circuit uses which method of measurement ?
a) absolute
b) relative
c) differential
d) comparison

View Answer

Answer: d [Reason:] A bridge circuit makes use of comparison measurement method.In this method the bridge compares the value of an unknown component with a standard value of a given component.

5. The principle on which a bridge circuit operates is
a) null indication
b) ampere’s rule
c) partial indication
d) kirchhoff’s laws

View Answer

Answer: a [Reason:] A bridge circuit operates on the principle of null indication. Based on the deflection of the galvanometer, current flows between the two opposite junctions.

6. The accuracy of a bridge depends on the _________
a) null indicator
b) bridge components
c) current source
d) voltage source

View Answer

Answer: b [Reason:] As a bridge circuit compares the value of an unknown component with the value of a standard, it’s accuracy depends on the bridge components.

7. When is the bridge circuit balanced ?
a) When voltage is applied
b) When current flows through the opposite ends of the bridge circuit
c) When no current flows through the galvanometer
d) When impedance is minimum

View Answer

Answer: c [Reason:] The bridge circuit is said to be balanced when no current flows through the null indicator which is generally a galvanometer.

8. Relationship at balance condition between the component values of the four arms of a bridge is known as
a) full load condition
b) open circuit condition
c) short circuit condition
d) balancing condition

View Answer

Answer: d [Reason:] During balance condition or equilibrium there exists a certain relationship between the component values of the four arms of the bridge. This relationship is known as the balancing condition or balancing equation.

9. D.C. bridges are used for _________
a) measurement of resistance
b) measurement of capacitance
c) measurement of current
d) measurement of inductance

View Answer

Answer: a [Reason:] Resistance measurements are done by making use of a suitable D.C. bridge.

10. What is used to characterise single port devices, multiport devices etc?
a) current values
b) impedance values
c) voltage values
d) power values

View Answer

Answer: b [Reason:] Impedance values are used to characterize one port devices, networks, multiport devices and other systems.

Set 3

1. Kelvin’s bridge consists of _________
a) double bridge
b) single bridge
c) half bridge
d) three fourth bridge

View Answer

Answer: a [Reason:] Kelvin’s bridge consists of two additional arms compared to a Wheatstone bridge. Hence it is also known as a double bridge.

2. The range of resistance measured in a Kelvin bridge is _________
a) 10Ω to 10 mΩ
b) 1Ω to 10 μΩ
c) 0.01Ω to 10 MΩ
d) 0.1Ω to 10 nΩ

View Answer

Answer: b [Reason:] Kelvin bridge is used for the measurement of low resistances. Low resistances vary in the range of 1Ω to 10 μΩ.

3. Accuracy of Kelvin bridge is of the order of _________
a) ±0.5 to ±2 %
b) ±0.05 to ±0.02 %
c) ±0.05 to ±0.2 %
d) ±0.005 to ±0.02 %

View Answer

Answer: c [Reason:] As Kelvin bridge is used for the measurement of low resistance values, the accuracy of measurement of low resistances in a Kelvin bridge is of the order of ±0.05 to ±0.2 %.

4. The balance equation of Kelvin bridge is
electrical-measurements-questions-answers-kelvin-bridge-q4

View Answer

Answer: d [Reason:] The balance equation in a Kelvin bridge is given by the relation Rx = R1R3R2. where, R1, R2, R3, and Rx form the ratio arms Rx is the value of the unknown resistance.

5. What is the effect of load and contact resistance in Kelvin bridge?
a) independent
b) fully dependent
c) partially dependent
d) depends on the resistance value

View Answer

Answer: a [Reason:] Effect of contact and lead resistances are completely eliminated in a Kelvin bridge as they don’t appear in the balance equation. Hence the Kelvin bridge is independent of the load and contact resistances.

6. The relation between ratio of resistance arms and ratio of resistance arms of second bridge is
a) unequal
b) equal
c) twice
d) one forth

View Answer

Answer: b [Reason:] The relation between the ratio of the resistances of resistance arm and second resistance arm is equal for balance condition.

7. Why Kelvin bridge is used for measurement of low resistance?
a) due to e.m.f source used
b) due to a large current flow
c) due to contact and lead resistance
d) due to power dissipation across the circuit

View Answer

Answer: c [Reason:] While measuring very low resistances the contact and lead resistances cause significant errors in the value of the measured resistance. As a result Kelvin bridge is used for measurement of low resistances.

8. What is the condition to achieve a high sensitivity in a Kelvin bridge?
a) low voltage
b) high power
c) medium resistance
d) high current

View Answer

Answer: d [Reason:] The condition to achieve a high sensitivity in a Kelvin bridge is that the measuring current should be high enough so as to sensitize the null detector.

9. Kelvin bridge can be calibrated to read
a) inductance and Quality factor value
b) capacitance only
c) power and voltage
d) current and frequency

View Answer

Answer: a [Reason:] In its basic form a Kelvin bridge is used for the measurement of low resistance. A Kelvin bridge can be used for the measurement of inductance and Quality factor value through calibration.

10. Why can’t a Kelvin bridge be used for the measurement of low Quality factor value?
a) due to thermoelectric effect
b) due to balance problem
c) due to the dull detector used
d) due to temperature

View Answer

Answer: b [Reason:] A Kelvin bridge can be used for the measurement of high Quality factor values. Due to bridge imbalance problem, Kelvin bridge can’t be used for measuring low Quality factor values.

Set 4

1. Maxwell inductance capacitance bridge can be used for _________
a) measurement of inductance
b) measurement of capacitance and inductance
c) measurement of resistance
d) measurement of voltage and current

View Answer

Answer: a [Reason:] A Maxwell inductance capacitance bridge is used for the measurement of inductance by making comparison with a standard capacitance value. Voltmeter is used to measure voltage, while an ammeter is used to measure current.

2. Balance equation for computing the unknown resistance is
electrical-measurements-questions-answers-maxwells-inductance-capacitance-bridge-q2

View Answer

Answer: b [Reason:] The balance condition for determining the value of the unknown resistance is given by the relation Rx = R2 R3R1. where, R1 and R3 are variable resistances and R2 is a fixed resistance.

3. Balance equation for computing the value of the unknown inductance is
a) Lx = R2 R3
b) Lx = R2 C1
c) Lx = R2 R3 C1
d) Lx = R3 C1

View Answer

Answer: c [Reason:] The balance equation for determining the value of the unknown inductance is given by the relation Lx= R2 R3 C1. where, C1 is the capacitance across the resistance R1 R3 is a variable resistance and R2 is a fixed resistance.

4. Quality factor of the circuit is given by _________
a) Q = ωC1
b) Q = ωR1
c) Q = ω
d) Q = ωR1 C1

View Answer

Answer: d [Reason:] The quality factor of a Maxwell inductance capacitance bridge is given by the relation electrical-measurements-questions-answers-maxwells-inductance-capacitance-bridge-q4

5. Standard inductor requires no shielding.
a) True
b) False

View Answer

Answer: b [Reason:] Stray magnetic fields are present in a circuit consisting of inductances and capacitances. In order to eliminate the stray magnetic fields proper shielding is required for the standard inductance.

6. Standard inductor provides rated inductance directly.
a) True
b) False

View Answer

Answer: b [Reason:] When the current flow through the standard inductance is adjusted precisely, it provides its rated value of inductance.

7. What is the significance of capacitors in a Maxwell bridge?
a) they are used to block dc
b) they are used to block ac
c) they are cheap
d) they are expensive

View Answer

Answer: c [Reason:] In a Maxwell inductance capacitance bridge, the capacitors are cheaper when compared to stable and accurate standard value of inductors.

8. The bridge balance equation can be written in _________
a) impedance form
b) resistance form
c) conductance form
d) admittance form

View Answer

Answer: d [Reason:] The bridge balance equation for a Maxwell inductance capacitance bridge consists of admittances. This is due to the connection of a capacitance in parallel across the resistance in one of the ratio arms.

Set 5

1. Low resistance refers to _________
a) resistances of the order of 1ῼ
b) resistances of the order of 1kῼ
c) resistances of the order of 1mῼ
d) resistances of the order of 1Mῼ

View Answer

Answer: a [Reason:] Low resistance refers to resistances of the order of 1ῼ or less than that. Medium resistances range from above 1ῼ to a few kῼ. Any resistance value greater than a few kῼ is known as a high resistance.

2. What is the significance of measuring low resistances?
a) voltage drop across the circuit is high
b) contact and lead resistances are appreciable
c) there is no power loss
d) no current flows through the bridge circuit

View Answer

Answer: b [Reason:] When measuring low resistances of the order of 1 ῼ or even less, lead and contact resistances of the order of even 0.002 ῼ cannot be neglected. High currents flow through low resistance circuits.

3. Fig 15.1 represents
electrical-measurements-questions-answers-measurement-low-resistance-q3
a) construction of medium resistance
b) construction of high resistance
c) construction of low resistance
d) construction of very low resistance

View Answer

Answer: c [Reason:] Fig 15.1, illustrates the construction of low resistance. A is an ammeter used to measure current through the circuit, while V is the voltmeter used to measure voltage.

4. How is the voltage drop across a low resistance related to lead resistance?
a) it contains contact resistance
b) it depends on the magnitude of voltage drop
c) it depends on the type of null detector used
d) It does not contain any contact resistance

View Answer

Answer: d [Reason:] The voltage drop measured across a low resistance does not contain any contact and lead resistances of the components and is independent of it.

5. Which is not a source of error in the measurement of low resistance?
a) contact resistance drops at the leads
b) thermal e.m.f
c) temperature effect
d) power dissipation through the circuit

View Answer

Answer: a [Reason:] As the current flowing through a low resistance circuit is low, the voltage drop across the terminals due to contact and lead resistances is negligible. Thermal e.m.f occurs in a circuit when its temperature increases due to high current flow.

6. Which is the most popular method for measuring low resistance?
a) ammeter-voltmeter method
b) potentiometer method
c) kelvin double bridge method
d) ducter ohmmeter method

View Answer

Answer: c [Reason:] Kelvin’s double bridge is used for the measurement of low resistances of the order of 1ῼ or less. Ammeter voltmeter method is used for the measurement of current flowing through and the voltage across the circuit.

7. How is the contact resistance related to the circuit while measuring a low resistance?
a) independant of the type of the resistance
b) it is negligible
c) depends on the e.m.f source
d) it is very high

View Answer

Answer: b [Reason:] The contact and lead resistances form a part of the circuit whose resistance is very high. As a result the contact and lead resistances are usually neglected compared to the high resistance value.

8. In fig 15.1, the terminals aa’ are used for
electrical-measurements-questions-answers-measurement-low-resistance-q3
a) measuring the current flow through the circuit
b) measuring the power dissipation of the circuit
c) measuring the resistance of the circuit
d) measuring the voltage drop across the resistance

View Answer

Answer: d [Reason:] The terminals aa’ are used for the measurement of the voltage drop across the resistance R. An voltmeter V is connected across the terminals aa’.

9. In the below figure, the value of I is _________
electrical-measurements-questions-answers-measurement-low-resistance-q9
a) I = IV + Ir
b) I = IV – Ir
c) I = IV Ir
d) I = IVIr

View Answer

Answer: a [Reason:] By applying Kirchhoff’s current law at the node N from fig we get, I = IV + Ir where, I is the total series current flowing through the circuit Iv is the current flowing through the voltmeter Ir is the current flowing through the resistance R.