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Multiple choice question for engineering

Set 1

1. Resistance temperature detector is ___________
a) a electrical transducer
b) a mechanical transducer
c) a chemical transducer
d) a physical transducer

View Answer

Answer: a [Reason:] Resistance temperature detector is an electrical transducer. It is used for measuring the variation in temperature. It is also known as a resistance thermometer.

2. Relation between temperature and resistance of a conductor is ________
a) Rt = Rref [1+t].
b) Rt = Rref [1+α∆t].
c) Rt = Rref [1-αt].
d) Rt = Rref [1-t].

View Answer

Answer: b [Reason:] The relationship between temperature and resistance of a conductor is given by Rt = Rref [1+α∆t]. where, Rt is the resistance of the conductor at t°C. Rref is the resistance of the conductor at reference temperature α is the temperature coefficient of resistance ∆t is the difference between the temperature being measured and the reference temperature.

3. Sensing element in the thermometer must provide ________
a) small change in resistance
b) no change in resistance
c) large change in resistance
d) infinite change in resistance

View Answer

Answer: c [Reason:] The sensing element in a thermometer must give a large change in the resistance for a given change in the temperature.

4. Platinum is used for industrial applications because ________
a) it is cheap
b) it is available readily
c) it is a noble metal
d) it gives accurate measurements

View Answer

Answer: d [Reason:] In industrial applications, platinum is used due to its accuracy in providing measurements. It is also reproducible. Platinum element can be used for the measurement of temperatures of about 1000 K.

5. Resistance thermometer provides the change in electrical resistance.
a) True
b) False

View Answer

Answer: a [Reason:] A resistance thermometer provides a change in the electrical resistance with respect to a variation in the temperature. Basically resistance thermometers work on the principle of change in the electrical resistance with variation in the temperature.

6. If the sensing element is large, then less amount of heat is required.
a) True
b) False

View Answer

Answer: b [Reason:] When the sensing element in a resistance thermometer is small in size, then less quantity of heat is required to raise the temperature. Platinum, nickel and copper are the commonly used metals for measuring temperature.

7. Most metallic conductors have a ________
a) neutral temperature coefficient of resistance
b) negative temperature coefficient of resistance
c) positive temperature coefficient of resistance
d) zero temperature coefficient of resistance

View Answer

Answer: c [Reason:] In general metallic conductors have a positive temperature coefficient of resistance. The resistance increases with an increase in the temperature.

8. In a temperature sensing element ________
a) low value of α is required
b) infinite value of α is required
c) α must be zero
d) high value of α is required

View Answer

Answer: d [Reason:] In order to achieve a large change in the value of resistance for a small change in the value of temperature, high value of α is required. Change in resistance is measured through a Wheatstone’s bridge.

9. Nickel and its alloys can be used over a temperature range of ________
a) 100 to 450 K
b) 10 to 50 K
c) 0 to 25 K
d) 5 to 15 K

View Answer

Answer: a [Reason:] Temperature sensors constructed using nickel and its alloys can be used in the temperature range of 100 to 450 K. Compared to platinum, they are less expensive. They have a comparatively higher temperature coefficient that increases with temperature.

10. How can corrosion be prevented in a resistance thermometer?
a) by immersing the setup in oil
b) by enclosing the elements in a glass tube
c) by using guard rings
d) by painting the elements

View Answer

Answer: b [Reason:] Corrosion can be eliminated in a resistance thermometer by enclosing the elements in a protective tubular glass made of pyrex, quartz or crystal depending upon the temperature range.

Set 2

1. Resolution of a DVM is given by
a) R = 110n
b) R = 1
c) R = 10n
d) R = n10

View Answer

Answer: a [Reason:] The resolution of a DVM is, R = 110n where, n is the number of full digits R is the resolution.

2. For a 3 digit display the resolution is
a) 1 %
b) 0.1 %
c) 0.001 %
d) 10 %

View Answer

Answer: b [Reason:] The resolution of a DVM is, R = 110n Here, n is 3. Substituting n=3 in the equation for resolution we get, R = 1103 = 10-3 = 0.001 = 0.1 %.

3. Sensitivity is largest change in input.
a) True
b) False

View Answer

Answer: b [Reason:] Sensitivity of any instrument is defined as the smallest hange in the input signal to which the output responds.

4. Sensitivity of a DVM is given by
a) S = 1
b) S = (fs)min
c) S = (fs)min × R
d) S = R

View Answer

Answer: c [Reason:] Sensitivity of the DVM is obtained from the relation, S = (fs)min × R where, S is the sensitivity R is the resolution (fs)min is the full scale value on minimum range.

5. The resolution of a 3 digit display on 1 V range is
a) 1 V
b) 0.1 V
c) 0.01 V
d) 0.001 V

View Answer

Answer: d [Reason:] The resolution of a DVM is, R = 110n Here, n is 3. Substituting n=3 in the equation for resolution we get, R = 1103 = 10-3 = 0.001 For 1 V range, the resolution is, R1V = 1×0.001 = 0.001 V.

6. How is 11.87 V displayed on a 10 V range for a 4 digit display?
a) 11.870
b) 1.1870
c) 118.7
d) 0.1187

View Answer

Answer: a [Reason:] The resolution of a DVM is, R = 110n Here, n is 4. Substituting n=4 in the equation for resolution we get, R = 1104 = 10-4 = 0.0001 Since there are 5 digit places in the resolution, 11.87 which already has four digits is represented as 11.870.

7. Consider a 3 digit display for a DVM with an accuracy of ± 0.5 % for a reading of ± 1 digit. Compute the error for 5 V reading on a 10 V range.
a) ± 10 V
b) ± 0.035 V
c) ± 0.05 V
d) ± 1 V

View Answer

Answer: b [Reason:] The resolution of a DVM is, R = 110n Here, n is 3. Substituting n=3 in the equation for resolution we get, R = 1103 = 10-3 = 0.001 For 10 V range, the resolution is, R10V = 10 × 0.001 = 0.01 V Consider the reading of 5 V. Error = ± 0.5 % of 5 = 0.5100 × 5 = ± 0.025 V 1 digit error = ± 0.01 V Total error = ±(0.025 V+ 0.01 V)=± 0.035 V.

8. Clock pulses are controlled ______
a) automatically
b) using microcontrollers
c) using valves
d) manually

View Answer

Answer: d [Reason:] A manual range hold command is used to control the clock pulses and the autoranging. This is done through a signal that exceeds the maximum range for up counts by reaching the most sensitive range (down counts).

Set 3

1. In general bridges consist of __________
a) lumped inductances
b) lumped resistances
c) distributed capacitance
d) distributed impedance

View Answer

Answer: a [Reason:] AC bridges in general such as Maxwell, Anderson, Schering etc consist of lumped components such as inductance.

2. Stray capacitance exists between the components.
a) True
b) False

View Answer

Answer: a [Reason:] In general in AC bridges, stray capacitance exists between the components of the bridge with respect to the ground. These stray capacitances short the ratio arms and lead to errors in the measurement.

3. The magnitude of stray capacitances is fixed.
a) True
b) False

View Answer

Answer: b [Reason:] Stray capacitances are uncertain in nature. Their magnitude depends on the adjustment of the bridge arms and the position of the operator.

4. Stray capacitance effects can be minimized by __________
a) making use of an inductance
b) connecting a resistance in series
c) shielding and grounding
d) using a galvanometer

View Answer

Answer: c [Reason:] The stray capacitance effects in an AC bridge can be eliminated by shielding and grounding. This method helps in making the stray capacitances constant in value. They can be compensated.

5. Most popular method of avoiding the stray capacitance effects is __________
a) by grounding
b) by using guard rings
c) by using galvanometer
d) by using Wagner device

View Answer

Answer: d [Reason:] A Wagner earthing device is used in general to eliminate the stray capacitance effects in AC bridges. The stray capacitance effects between the components in the ratio arms with respect to ground can be eliminated through this method.

6. Wagner device is a ____________
a) capacitance bridge
b) resistance bridge
c) inductance bridge
d) impedance bridge

View Answer

Answer: a [Reason:] A Wagner earth device is generally used for shielding and grounding purpose. It consists of capacitances in the ratio arms along with a series RC combination connected across the ends of the bridge forming a potential divider.

7. Which is the guarding arm?
a) parallel RC combination
b) series RC combination
c) resistance R
d) capacitance C

View Answer

Answer: b [Reason:] The series combination of R and C in a Wagner earth device forms a potential divider across the ratio arms. It is also known as the guard arm.

8. Bridge is suitable for _________
a) coils with high Q values
b) coils with low Q values
c) coils with intermediate Q values
d) coils with very high Q values

View Answer

Answer: b [Reason:] The Maxwell inductance capacitance bridge is basically used for the measurement of Quality factor (Q) of inductance coils with low Q values.

Set 4

1. Range of an electrical instrument depends on __________
a) current
b) voltage
c) power
d) resistance

View Answer

Answer: a [Reason:] The amount of current safely passing through the coil of the instrument and the spiral springs. This acts as the leads of the current to the instrument. As a result, the range of an electrical instrument depends on the current.

2. Moving coil instruments have a current and voltage rating of __________
a) 100 A and 25 V
b) 50 mA and 50 mV
c) 75 nA and 100 μV
d) 25 μA and 75 V

View Answer

Answer: b [Reason:] Moving coil instruments are designed to function as Ammeters and Voltmeters. They have a maximum current carrying capacity of 50 mA with a voltage rating of 50 mV.

3. A shunt is a __________
a) very high resistance
b) medium resistance
c) very low resistance
d) high resistance

View Answer

Answer: c [Reason:] Usually shunt is a very low value of resistance. It is connected in parallel with the ammeter coil. Through this we can extend the range of an ammeter.

4. A shunt can be used to measure large currents.
a) True
b) False

View Answer

Answer: a [Reason:] A shunt is normally a very low value of resistance, connected in parallel with the ammeter coil. By making use of a low range ammeter, large current values can be measured through a shunt.

5. Current terminals have a small current capacity.
a) True
b) False

View Answer

Answer: b [Reason:] A shunt is normally a very low value of resistance, connected in parallel with the ammeter coil. In a shunt, the current terminals have a large current capacity and are connected in series.

6. Potential terminals have a __________
a) high current capacity
b) low voltage capacity
c) low current capacity
d) high voltage capacity

View Answer

Answer: c [Reason:] A shunt is normally a very low value of resistance, connected in parallel with the ammeter coil. In a shunt, the potential terminals have a low current carrying capacity. As a result, a low range ammeter is used to measure the large current.

7. In case of AC ammeters, shunts consist of __________
a) impedance
b) capacitance
c) resistance
d) inductance

View Answer

Answer: d [Reason:] AC ammeter shunts comprise of the inductances of the ammeter as well as the shunt. In order to extend the range of an AC ammeter, inductances of the ammeter and the shunt are taken into account.

8. What is the effect of the ammeter range on the shunt resistance?
a) no effect
b) varies by a factor of multiplying factor
c) varies by a factor of the resistance
d) varies by a factor of unity

View Answer

Answer: b [Reason:] We know that N = 1 + RaRs where, N is the multiplying factor Ra is the ammeter resistance Rs is the shunt resistance It is clear from the above equation that in order to increase the ammeter range by N times, the shunt resistance is equivalent to 1N-1.

9. A multiplier is __________
a) non-inductive
b) resistive
c) capacitive
d) non-capacitive

View Answer

Answer: a [Reason:] A multiplier is basically a non-inductive, high resistance that is used to extend the range of a D.C. voltmeter. Multiplier consists of a low range D.C. voltmeter connected in series with it.

10. What is the condition for using a multiplier in A.C. voltmeters?
a) by using ac supply
b) by maintaining a uniform impedance
c) by maintaining a uniform frequency
d) by using a galvanometer

View Answer

Answer: c [Reason:] A multiplier can be used for A.C. voltmeters. The condition to be satisfied is that the total impedance of the voltmeter and the multiplier circuit must be constant for a wide range of frequencies.

Set 5

1. What is the role of CRT?
a) to emit electrons
b) to emit protons
c) to emit neutrons
d) to emit alpha particles

View Answer

Answer: a [Reason:] Cathode ray tube forms the heart of a C.R.O. It is used to emit electrons so as to strike the phosphor screen to produce a spot for the visual display of the signals.

2. Input signals are amplified using ___________
a) rectifier
b) amplifier
c) oscillator
d) op amp

View Answer

Answer: b [Reason:] Vertical amplifier is used in a cathode ray tube to amplify the input signals. Magnitude of the input signal is weak and not sufficient enough to give deflection on the screen.

3. Amplifier stage is ___________
a) half band
b) full band
c) wide band
d) narrow band

View Answer

Answer: c [Reason:] Wide band amplifiers are generally used to amplify the input signals. The whole band of frequency to be measured must be passed faithfully by making use of a wide band amplifier.

4. Role of an attenuator is ___________
a) to boost the signal
b) to distort the signal
c) to remove noise
d) to improve the operation

View Answer

Answer: d [Reason:] When we need to measure very high voltage signals, attenuator stages are used. This is done in order to bring the signal level within the range of operation of the amplifier.

5. Amplifier is multiple stage in a CRO.
a) True
b) False

View Answer

Answer: a [Reason:] A Cathode Ray Tube essentially consists of multiple stages of amplifiers with a overall fixed sensitivity. Amplifier is designed for stability and required bandwidth very easily due to the fixed gain.

6. Input stage in the amplifier consists of ___________
a) oscillator
b) attenuator
c) rectifier
d) op amp

View Answer

Answer: b [Reason:] The amplifier stage of a Cathode Ray Tube essentially consists of an attenuator stage. It is followed by a FET source follower. The input impedance is very high.

7. Phase inverter is used in an amplifier in the CRO because ___________
a) phase inversion is needed
b) no phase inversion is needed
c) it is needed to operate a push pull
d) it provides voltage stability

View Answer

Answer: c [Reason:] In a Cathode Ray Oscilloscope, phase inverter is typically used for operating a push pull amplifier. It provides two antiphase output signals in order to operate the push pull amplifier.

8. BJT is used in the amplifier stage.
a) True
b) False

View Answer

Answer: a [Reason:] A BJT emitter follower is used in the amplifier stage after the FET in order to provide impedance matching to the output of the FET. With respect to the input of the phase-inverter.

9. Why is a delay line used in a CRO?
a) to boost the signal
b) to distort the signal
c) to provide signal delay
d) for stability

View Answer

Answer: c [Reason:] Delay line is used in a Cathode Ray Oscilloscope so as to delay the signal for some time. If the delay line is not used then a part of the signal is lost. A delay line circuit is used for this purpose.