Multiple choice question for engineering
1. What is hold off time in a CRO?
a) time to start a ramp
b) time to end a ramp
c) time to start a unit step
d) time to end a unit step
Answer: a [Reason:] In a Cathode Ray Oscilloscope, the trigger circuit applies the pulse as soon as the cycle ends. The hold off time in a time base generator is defined as the time taken for the ramp signal so as to stabilise the flyback circuitry.
2. What is wait time in a CRO?
a) time to deactivate time base generator
b) time to activate time base generator
c) time from input to output
d) time from output to input
Answer: b [Reason:] In a Cathode Ray Oscilloscope, the trigger circuit produces a trigger pulse. The pulse must exceed a certain reference threshold level in order to activate the time base generator. This is known as trigger threshold.
3. A trigger circuit is ___________
a) is used for triggering the input
b) is used for triggering the output
c) used with time base generator
d) used as a oscillator
Answer: c [Reason:] In a Cathode Ray Oscilloscope, the trigger circuit is basically used for triggering the time base generator. It triggers the time base generator and produces a ramp signal.
4. Time base generator takes certain time to begin a new cycle.
Answer: a [Reason:] After the end of a cycle of sweep and retrace, the time base generator takes certain amount of time to commence a new cycle. This time can be divided into two parts:
i) Hold off time and ii) Waiting time.
5. After hold off time, the time base generator is activated immediately.
Answer: b [Reason:] As a result of trigger threshold crossing the time base generator doesn’t immediately get activated after the hold off time. This time is known as the waiting time wherein the triggering pulses cross the trigger threshold.
6. A time base should have _________
b) ramp relationship
d) unit step relationship
Answer: c [Reason:] In a Cathode Ray Oscilloscope, a time base generator must have a linear relationship. A linearity of the order of more than 1 % across the cathode ray tube can be obtained by making use of a time base generator.
7. The horizontal amplifier in a CRO can be expanded by _________
a) 5 times
b) 15 times
c) 30 times
d) 10 times
Answer: d [Reason:] In a Cathode Ray Oscilloscope, the horizontal amplifier can be expanded by upto 10 times. This allows a division of 1nsec display for very high speed transient waveforms.
8. Sweep rate is controlled by a _________
Answer: a [Reason:] In a Cathode Ray Oscilloscope, the sweep rate is controlled by a capacitor. This is done through means of the charging current flowing through the capacitor.
1. The main objective of a process control is _________
a) to control physical parameters
b) to control mechanical parameters
c) to control optical parameters
d) to control electrical parameters
Answer: a [Reason:] A process control is mainly used in order to control the physical parameters including temperature, pressure, flow rate, force, etc.
2. What is a process control system?
a) system to keep the parameters at zero value
b) system to maintain the parameters constant
c) system to keep the parameters at highest value
d) system to check the voltage
Answer: b [Reason:] A process control system is generally used to maintain the parameters such as temperature, pressure, flow rate, force, etc constant in a system.
3. Physical parameters change due to ________
c) internal and external disturbances
Answer: c [Reason:] The physical parameters such as temperature, pressure, flow rate, force, etc in a process control system are affected due to both internal and external disturbances. As a result, constant corrective action is required to keep them at a constant value.
4. A process control system consists of ________
a) 10 elements
b) 6 elements
c) 2 elements
d) 4 elements
Answer: d [Reason:] A typical process control system consists of 4 elements. They are as follows:
• Control element
The figure shown below illustrates the process control loop.
5. For proper feedback in a process control element, it is required to ________
a) measure P
b) measure set point
c) measure error
d) measure comparator
Answer: a [Reason:] In a process control element, proper feedback is obtained by measuring the parameter P. Electrical input is required in most of the process controllers as they are electronic in nature.
6. Feedback path element measure only input parameters.
Answer: b [Reason:] In a process control system, feedback path measures the output parameters. It also produces a proportional analog signal in electric form.
7. A transducer converts ________
a) mechanical quantity to electrical form
b) electrical quantity to physical form
c) physical quantity to electrical form
d) chemical quantity to physical form
Answer: c [Reason:] A transducer basically converts a physical quantity such as temperature, pressure, force, flow rate, etc into electrical form such as voltage and current.
8. An electrical transducer consists of ________
a) 4 parts
b) 6 parts
c) 8 parts
d) 2 parts
Answer: d [Reason:] An electrical transducer basically consists of 2 parts. The first is known as the sensing element while the second is known as the transduction element. The first element is also known as a sensor.
9. A transducer is part of a large circuit and produces the required output.
Answer: a [Reason:] A transducer basically converts a physical quantity such as temperature, pressure, force, flow rate, etc into electrical form such as voltage and current. A transducer is part of a large circuit. It produces the required output by operating along with several other elements.
1. Q factor is called __________
a) Quality factor
b) Quantity factor
c) Queen factor
d) Quarter factor
Answer: a [Reason:] Q factor is also known as Quality factor or storage factor. It is basically a ratio of the power stored in an element to the power dissipated in that element.
2. Q factor is also defined as the ratio of _______
a) resistance to reactance
b) reactance to resistance
c) power to voltage
d) current to power
Answer: b [Reason:] Q factor can also be obtained as the ratio of reactance to resistance of an element. For inductive element it is the ratio of XL to R and for a capacitive element it is the ratio of XC to R.
3. What is a Q meter?
a) quality meter
b) quantity meter
Answer: c [Reason:] Q meter is basically an instrument that is used for the measurement of electrical properties of capacitors and coils. It is also used as a laboratory instrument.
4. Q meter works on the principle of _______
a) barkhausen criterion
b) piezoelectric effect
c) parallel resonance
d) series resonance
Answer: d [Reason:] Q meter basically operates on the characteristics of a series resonant coil. In a series resonant circuit the voltage drop across the coil or a capacitor is equal to the applied voltage multiplied by its Q factor.
5. Q factor for a series resonant circuit is
Answer: a [Reason:] Q factor in a series resonant circuit is given by the relation,
Q = XL⁄R = XC⁄R where, R is resistance of the coil
XC is the capacitive reactance
XL is the inductive reactance.
6. What is the relation between Q factor and voltage?
Answer: b [Reason:] The applied voltage E is inversely proportional to the Q factor of a circuit and is given by the relation,
7. A practical Q meter consists of __________
a) Wien bridge oscillator
b) AF oscillator
c) RF oscillator
d) Crystal oscillator
Answer: c [Reason:] Practically a Q meter consists of a wide range RF oscillator with a frequency range of 50 kHz to 50 MHz. Oscillator acts as a source and delivers current to a low shunt resistance.
8. Voltage across the shunt is measured by ________
Answer: c [Reason:] A thermocouple is used for measuring the voltage across a shunt resistance in a practical Q meter. Electronic voltmeter is used for the measurement of voltage across a resonant capacitor.
9. Inductance of the coil is ________
Answer: d [Reason:] Coil inductance in a Q meter is given by the relation,
where, f is the frequency in Hz
C is the capacitance in F.
1. Electronic recorders are of __________
a) 2 types
b) 4 types
c) 10 types
d) 15 types
Answer: a [Reason:] Electronic recorders are of two types. They are as follows:
• Analog recorders
• Digital recorders.
2. Non-electrical quantities are measured directly.
Answer: b [Reason:] All non-electrical quantities are measured indirectly. The non-electrical quantities are converted into their equivalent voltages or currents using different transducers.
3. A physical quantity is recorded to preserve the details.
Answer: a [Reason:] Physical quantity is recorded so as to preserve some of the details of the quantity with time.
4. How many types of graphic recorders are there?
Answer: c [Reason:] There are three types of graphic recorders. They are as follows:
• Strip chart recorder
• Circular chart recorder
• X-Y recorder.
5. Recorder is a ________
a) measuring instrument
b) voltage source
c) current divider
d) musical tool
Answer: a [Reason:] Recorder is a measuring equipment. A recorder is used to measure time varying quantities even if the quantity has stopped.
6. Efficiency of a recorder is determined using ________
Answer: b [Reason:] The recorder efficiency is determined by means of a chart. Generally chart recorders are of three types. They are X-Y recorder, strip chart recorder and a circular chart recorder.
7. In a strip chart recorder ________
a) biological quantity is measured
b) chemical quantity is measured
c) physical quantity is measured
d) no quantity is measured
Answer: c [Reason:] A strip chart recorder measures a physical quantity by making use of a continuous roll of chart paper at a constant speed.
8. Basic elements of a strip chart recorder are ________
a) chalk and board
b) pen and pencil
c) pencil and paper
d) pen and chart paper
Answer: d [Reason:] The basic elements of a strip chart recorder are pen and chart paper for recording data. Input data is recorded on a chart paper through the following methods:
• Pen and ink stylus
• Impact printing
• Chopper bar printing
• Thermal writing
• Electric writing
• Optical writing.
9. How many types of tracing systems are used in graphical representation?
Answer: a [Reason:] There are two types of tracing systems used in graphical representation. They are as follows:
• Curvilinear System
• Rectilinear System.
10. A galvanometer based recorder works on the principle of ________
a) Van der Wall’s effect
b) D’Arsonval movement
c) Paschen effect
d) Azhimuthal quatum number
Answer: b [Reason:] D’Arsonval movement forms the basis for the working of a galvanometer type recorder. When current passes through the coil, deflection is produced by the galvanometer.
1. Ramp type DVM uses
a) a linear ramp technique
b) a non-linear ramp technique
c) an exponential ramp technique
d) an asymptotic ramp technique
Answer: a [Reason:] A ramp type DVM makes use of a staircase ramp technique or a linear ramp technique. Compared to the linear ramp technique, the staircase ramp technique is much simpler.
2. Linear ramp technique is based on
a) voltage measurement
b) time measurement
c) current measurement
d) resistance measurement
Answer: b [Reason:] Linear ramp technique works on the principle of measurement of time required by a linear ramp to rise from 0 V to the input voltage. It can also be the time required by the input voltage to fall to 0 V.
3. Time is measured using
b) logic gates
Answer: c [Reason:] An electronic counter is used for the measurement of time in the linear ramp technique. A digital display is used to show the numerical value of time.
4. Which is the main device used in the linear ramp technique?
a) exponential ramp
b) asymptotic ramp
c) non-linear ramp
d) linear ramp
Answer: d [Reason:] The linear ramp technique essentially consists of a linear ramp. It is either positive or negative going. Range of the linear ramp varies from –12 V to +12 V. Base range varies from –10 V to +10 V.
5. Resolution depends on
Answer: a [Reason:] In the linear ramp technique, resolution is dependent on the frequency of the local oscillator. By adjusting the frequency of the local oscillator the resolution of the linear ramp can be made higher.
6. How is input voltage measured?
a) by using a voltmeter
b) by counting the pulses
c) by using a multimeter
d) by using a transformer
Answer: b [Reason:] The electronic counter used in the linear ramp technique counts the definite number of pulses during the start and end pulse. This count is a measure of the input voltage signal.
7. Which determines the rate of measurement cycles?
Answer: c [Reason:] Initiation of the measurement cycles is taken care of by the sample rate multivibrator. This vibrator oscillates at the rate of 1000 cycles per second. It is adjusted by a front panel control.
8. Typical value of the multivibrator is
a) 10 cycles/second
b) 0.2 cycles/second
c) 50 cycles/second
d) 5 cycles/second
Answer: d [Reason:] A multivibrator has a typical value of 5 cycles/second. It has an accuracy of the order of ±0.005 %. The ramp generator starts the next ramp voltage based on the sample rate.
9. Swing of the ramp is
a) ±12 V
b) ±10 V
c) ±8 V
d) ±5 V
Answer: a [Reason:] In the linear ramp technique, a swing of ±12 V is produced by the ramp. This limits the effective voltage available to ±10 V considering the voltage drop across the components in the circuit.