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Multiple choice question for engineering

Set 1

1. Digital multimeter is used for _________
a) measuring a.c. and d.c. current, voltage and resistance
b) measuring a.c. current and voltage
c) measuring d.c. current and resistance
d) measuring a.c. voltage and resistance

View Answer

Answer: a [Reason:] Digital multimeter is usually used for the measurement of a.c. current, voltage and resistance. It is also used for the measurement of d.c. current, voltage and resistance as well over several range.

2. Current is converted to voltage __________
a) through a voltmeter
b) through a resistance
c) through an ammeter
d) through a galvanometer

View Answer

Answer: b [Reason:] Current is passed through a low shunt resistance and is converted to voltage. A.C. quantities are converted to D.C. through various rectifier and filter circuits. Voltmeter and ammeter are used for voltage and current measurement respectively.

3. For resistance measurement, meter contains _________
a) high current source
b) medium current source
c) low current source
d) low voltage source

View Answer

Answer: c [Reason:] Usually in the measurement of resistance, meter consists of a precision low current source applied across an unknown resistance which gives a d.c. voltage.

4. Quantities are digitised using _________
a) D/A converter
b) oscillator
c) amplifier
d) A/D converter

View Answer

Answer: d [Reason:] Quantities such as current, voltage and resistance are digitised by making use of an A/D converter. They are then displayed on the screen by making use of a digital display.

5. Analog mulimeters require power supply.
a) True
b) False

View Answer

Answer: b [Reason:] Analog multimeters are less affected by electric noise and isolation problems. As a result analog multimeters don’t require a power supply.

6. Output of a digital multimeter is _________
a) mechanical
b) optical
c) electrical
d) analog

View Answer

Answer: c [Reason:] Digital multimeter gives an electrical signal as the output. A/D converter is employed for the conversion from analog to digital signal. This can be used for interfacing with external equipment.

7. Basic building blocks of digital multimeter are _________
a) oscillator, amplifier
b) diode, op amp
c) rectifier, schmitt trigger
d) A/D, attenuator, counter

View Answer

Answer: d [Reason:] Usually dual slope integrating type ADC is preferred in multimeter. It basically consists of several A/D converters, counter circuits and an attenuation circuit.

8. Resistance is measured using _________
a) constant current source
b) constant voltage source
c) variable current source
d) variable voltage source

View Answer

Answer: a [Reason:] Constant current source is used to measure resistance in a digital multimeter. Standard known value of current is passed through an unknown resistance and the drop in voltage across the resistance is measured.

9. A.C. voltages are measured using _________
a) oscillators and op amps
b) rectifiers and filters
c) resistor and capacitor
d) inductor and resistor

View Answer

Answer: b [Reason:] Rectifiers and filter circuits with various configurations are employed for measuring A.C. voltages. A.C. is converted to D.C. and is applied to the A/D converter.

Set 2

1. What is the main advantage of using a digital storage oscilloscope?
a) uses digital storage
b) uses analog storage
c) uses mixed mode storage
d) uses disc storage

View Answer

Answer: a [Reason:] The disadvantage of a analog storage oscilloscope is overcome in a digital storage oscilloscope. The unreliable storage method in a analog storage oscilloscope is overcome in a digital storage oscilloscope. The digital storage oscilloscope makes use of digital storage for the memory.

2. The memory of a digital storage oscilloscope is limited.
a) True
b) False

View Answer

Answer: b [Reason:] In a digital storage oscilloscope, the memory can store data as long as required without degradation. It makes use of complex signal processing techniques through high speed digital signal processing.

3. The waveform is stored in _________
a) compressed form
b) analog form
c) digital form
d) mixed form

View Answer

Answer: c [Reason:] The waveform to be studied is stored in digital form in the digital storage oscilloscope. It is digitized and stored in a digital memory.

4. Which oscilloscope is used in a digital storage oscilloscope?
a) multi trace
b) dual trace
c) modern
d) conventional

View Answer

Answer: d [Reason:] A digital storage oscilloscope makes use of a conventional cathode ray tube. As a result, the cost is reduced.

5. Power requirement is _________
a) low
b) high
c) medium
d) zero

View Answer

Answer: a [Reason:] In a digital storage oscilloscope, the power required by the memory is less. It can be supplied through the means of a small battery.

6. The stored image can be displayed _________
a) for a limited time
b) for infinite time
c) for zero time
d) for an intermediate time

View Answer

Answer: b [Reason:] In a digital storage oscilloscope, the stored image can be displayed for a long time as long as the power supply to the digital memory is kept intact without any kind of disruption.

7. The analog signal is digitized using _________
a) D/A converter
b) Oscillator
c) A/D converter
d) Rectifier

View Answer

Answer: c [Reason:] In a digital storage oscilloscope, the analog signal is digitized by making use of an analog to digital converter. After digitizing the waveform is loaded into a computer and can be analyzed.

8. How is the data displayed?
a) through a screen
b) through a computer
c) through an FPGA
d) through a microprocessor

View Answer

Answer: d [Reason:] In a digital storage oscilloscope, the data is displayed by passing it through a microprocessor which processes the data and displays the waveform onto a screen.

9. A digital storage oscilloscope has _________
a) 3 modes
b) 2 modes
c) 4 modes
d) 5 modes

View Answer

Answer: a [Reason:] In a digital storage oscilloscope, there are three modes of operation. They are as follows: • Store • Roll • Hold or Save.

Set 3

1. Digital voltmeters converts ________
a) analog to digital signal
b) digital to analog signal
c) current to voltage
d) resistance to voltage

View Answer

Answer: a [Reason:] In general digital voltmeters are known as DVM. They convert analog signals into digital voltage. They also display the voltage to be measured in the form of discrete numerals in place of pointer deflection.

2. Digital voltmeters can be used to measure ________
a) voltage only
b) voltage, temperature, pressure etc.
c) voltage and current
d) voltage and resistance

View Answer

Answer: b [Reason:] Digital voltmeters are used for the measurement of A.C. as well as D.C. voltages and also to measure physical quantities such as temperature, pressure, stress etc. through the use of appropriate transducer and signal conditioning circuits.

3. A digital voltmeter reduces parallax error.
a) True
b) False

View Answer

Answer: a [Reason:] A digital voltmeter minimizes the errors due to human interference, interpolation mismatch and errors due to parallax. A digital display is used to show the output voltage on a front panel.

4. In a DVM, a transducer converts ________
a) input to proportional current
b) input to proportional power
c) input to proportional voltage
d) input to proportional resistance

View Answer

Answer: c [Reason:] In a digital voltmeter, a transducer is used. In general a transducer converts a physical quantity into an electrical signal. In a DVM the transducer converts the input signal into proportional voltage.

5. In a DVM, a signal conditioning circuit is used ________
a) to bring current to a suitable limit
b) to bring resistance to a suitable limit
c) to bring resistance to s suitable limit
d) to bring voltage to a suitable limit

View Answer

Answer: d [Reason:] In a DVM, signal conditioning circuit is used. It converts the input signal into an voltage of suitable limit. This is done so that the voltmeter can read the magnitude of the signal correctly.

6. Input range of DVM is _________
a) 1 V to 1000 V
b) 0.1 V to 10 V
c) 0.01 V to 1 V
d) 0.001 V to 0.1 V

View Answer

Answer: a [Reason:] In a DVM, the input voltage range is given as 1 V to 1000 V. It includes automatic range selection and overload indication.

7. Output in digital form can’t be used directly.
a) True
b) False

View Answer

Answer: b [Reason:] The output obtained from a DVM can be used directly. It can be recorded and is also suitable for further processing.

8. What is the effect of IC chips on DVM?
a) increase in cost
b) increase in power
c) reduction in cost
d) increase in size

View Answer

Answer: c [Reason:] Advancement in IC chips have ensured the reduction in cost of the DVM’s. Size and power needs of DVM’s have been reduced by a huge margin.

Set 4

1. Why is dual slope method preferred over ramp techniques?
a) no noise
b) partial noise
c) average noise
d) maximum noise

View Answer

Answer: a [Reason:] During the process of integration, noise is cancelled out by the positive and negative ramps in the dual slope method. The input signal is integrated only for a fixed interval of time and this is the basis for the dual slope method.

2. What is the significance of the name dual slope method?
a) it has two slopes
b) it integrates the input twice
c) it uses two inputs
d) it has two outputs

View Answer

Answer: b [Reason:] The input signal is integrated only for a fixed interval of time and this is the basis for the dual slope method. Reference voltage is integrated with a negative slope. Hence the method is known as dual slope integrating type DVM.

3. The output voltage in a dual slope integrating type DVM is
a) differential of the input
b) multiple of the input
c) integral of the input
d) zero

View Answer

Answer: c [Reason:] In a dual slope integrating type DVM, the output voltage is given by the integral of the input voltage. electrical-measurements-questions-answers-dual-slope-integrating-type-dvm-q3 where, Vin is the input voltage R1 is the series resistance t1 is the time for which the capacitor is charged.

4. Input voltage depends on
a) resistance
b) capacitance
c) current
d) time-period

View Answer

Answer: d [Reason:] The input voltage in a dual slope integrating type DVM is given by the relation, Vin = Vref t2t1 From the above equation it is seen that the input voltage in a dual slope integrating type DVM depends on the time periods t1 for which the capacitor is charged and t2 during which the capacitor is discharged.

5. Noise rejection is poor.
a) True
b) False

View Answer

Answer: b [Reason:] In a dual slope integrating type DVM, the noise is cancelled out by the positive and negative ramps during the process of integration. As a result, the noise rejection is excellent.

6. What is the effect of the capacitor on the output?
a) no effect
b) charging effect
c) electrostatic effect
d) magnetic effect

View Answer

Answer: a [Reason:] In the dual slope integrating type DVM method, the capacitor is connected through means of an electronic switch. As a result the effects due to offset voltage wherein there exists an output voltage without the application of any input are eliminated.

7. What is the effect of clock on the voltage?
a) voltage doubles with clock input
b) voltage halves with clock input
c) no effect
d) voltage becomes zero with clock input

View Answer

Answer: c [Reason:] In a dual slope integrating type DVM, the value of the unknown voltage is independent of the frequency of the clock. It depends only on the number of counts read by the electronic counter.

8. Counter value at the beginning is
a) one
b) ten
c) three
d) zero

View Answer

Answer: d [Reason:] In a dual slope integrating type DVM, the electronic counter is reset to 0 at the beginning of the measurement of voltage. Flip-flop output is also maintained at zero and is given to a control logic.

9. What is the maximum count of the counter?
a) 9999
b) 0
c) 500
d) 1000

View Answer

Answer: a [Reason:] In a dual slope integrating type DVM, the electronic counter reaches a maximum value of 9999 before resetting. A carry pulse is generating pulling down all the digits to zero. Flip-flop then activates the control logic.

Set 5

1. Why a dual slope oscilloscope is needed?
a) to compare more than two voltages
b) to measure the voltage
c) to measure the current
d) to measure the time

View Answer

Answer: a [Reason:] A dual trace oscilloscope is required for comparison for two or more voltages in the analysis and study of electronic circuits and systems.

2. What is the problem with using more than one oscilloscopes?
a) measuring the signal’s parameters
b) triggering
c) supply voltage
d) errors in reading

View Answer

Answer: b [Reason:] When one more than one oscilloscope is used, the trigger sweeps of each can’t be synchronized simultaneously. As a result dual trace oscilloscopes are used in order to save the cost.

3. Independent traces can be obtained using
a) 4 methods
b) 6 methods
c) 2 methods
d) 8 methods

View Answer

Answer: c [Reason:] In order to generate two independent traces in a oscilloscope, two methods are used. One method is known as the sweep method whereas the other is known as the chop method.

4. Two methods are used to generate independent traces.
a) True
b) False

View Answer

Answer: a [Reason:] In a Cathode Ray Oscilloscope, two methods are used to generate two independent traces. The first method is an alternate sweep method while the second is the chop method.

5. How many vertical inputs exist in a dual trace oscilloscope?
a) 8
b) 6
c) 4
d) 2

View Answer

Answer: d [Reason:] In a Dual Trace Oscilloscope, two vertical inputs exist. The two channels are known as A and B. A separate preamplifier and an attenuator stage exist for each channel. The amplitude of each input can be controlled separately.

6. After pre-amplification the signals are fed into
a) an electronic switch
b) a signal generator
c) a rectifier
d) a regulator

View Answer

Answer: a [Reason:] In a Dual Trace Oscilloscope, after the pre amplification process is done, the signals are fed into an electronic switch. The switch passes one channel at a time through the delay line.

7. X-Y mode means
a) 2 modes
b) vertical and horizontal
c) x axis and y axis
d) ground and full line supply

View Answer

Answer: b [Reason:] In a Dual Trace Oscilloscope, X-Y mode means the oscilloscope operates from the first channel A as a vertical signal and from the second channel B as a horizontal signal.

8. Electronic switch is controlled by
a) D flip-flop
b) SR flip-flop
c) T flip-flop
d) JK flip-flop

View Answer

Answer: c [Reason:] In the Dual Trace Oscilloscope, an electronic switch is controlled by making use of a T flip-flop which is also known as a toggle flip-flop. Switching occurs during the beginning of a new sweep.

9. Which technique of a Dual Trace Oscilloscope maintains the phase between the signals?
a) Analog mode
b) Mixed mode
c) Chop mode
d) Alternate mode

View Answer

Answer: d [Reason:] In a Dual Trace Oscilloscope, the alternate mode of operation enables to maintain the correct phase relationship between the signals from the channels A and B.