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# Multiple choice question for engineering

## Set 1

1. What will be the transfer function of a body of mass M, in which input quantity is force and output quantity is displacement?
a) sM
b) s2M
c) 1/sM
d) 1/( s2 M)

Answer: d [Reason:] Force can be described as the product of mass and acceleration, or in terms of displacement F= M(dx2 (t)) / (dt2 ). Converting to Laplace domain and finding transfer function we obtain the answer.

2. Mass and Moment of inertia are equivalent quantities.
a) True
b) False

Answer: a [Reason:] Differential equation of torque is given as T=j(dθ2(t)) / (dt2 ) and differential equation corresponding to force is given as F= M(dx2(t))/(dt2 ) . Equating these two expressions we obtain mass ‘M’ and moment of inertia ‘j’ are equivalent quantities.

3. Linear and torsional springs are used to provide ________________and __________________
a) Restoring force and torque respectively
b) Restoring torque and force respectively
c) Restoring torque only
d) None of the mentioned

Answer: a [Reason:] Linear springs are used to provide restoring force and torsional springs are used to provide restoring torque respectively.

4. Restoring force of a spring under stress is F(s) = ____________
a) X(s)
b) KX(s)
c) K
d) None of the mentioned

Answer: b [Reason:] Restoring force of a spring under stress is given by KX(s), where K is the stiffness of spring and X(s) is the displacement made.

5. Spring is a ___________ order system.
a) Zero
b) First
c) Second
d) Third

Answer: a [Reason:] From transfer function of spring, it is clear that spring is a zero order system. Transfer function (F(s)) / (G(s))=K.

6. Name the Friction which acts till the body starts moving?
a) Dynamic friction
b) Static friction
c) Viscous friction
d) None of the mentioned

Answer: b [Reason:] Static friction is a constant value and is the minimum force required to start motion of a body.

7. What will you call the friction between a relative motions of two bodies?
a) Static friction
b) Dynamic friction
c) Viscous friction
d) None of the mentioned

Answer: c [Reason:] Viscous friction acts when there is a relative motion between two bodies. It always acts opposite to direction of velocity.

8. What is the equivalent quantity of capacitance in transfer function of viscous force?
a) Viscous force
b) Viscosity
c) Damping coefficient
d) Inertia

Answer: c [Reason:] Transfer function of viscous force is given as 1/sB, and transfer function of capacitor is given as 1/sC. On equating B and C becomes equivalent quantities.

9. Transfer function of force acting on a body is given as 1/(s2 M). What will be the transfer function of rotating body?
a) 1/(s2 j)
b) 1/j
c) 1/sM
d) None of the mentioned

Answer: a [Reason:] Mass M and Moment of inertia j are equivalent, thus transfer function of rotational motion can be obtained by replacing M with j.

10. 20N force is acting on a 5Kg body. What will be its rate of change of velocity?
a) 4m/s2
b) 5m/s2
c) 10m/s2
d) 2m/s2

Answer: a [Reason:] Rate of change of velocity is acceleration and force can be described as product of mass and acceleration.

## Set 2

1. Phase difference between two voltages at frequencies above 10Hz can be measured using:
a) CRO
b) Voltmeter
c) X-Y plotter
d) Multi meter

Answer: a [Reason:] For signals with frequencies greater than 10Hz, phase angle can be measured using CRO. Two signals are applied on two channels and phase difference is measured from screen.

2. What is the operating range of X-Y plotter?
a) Below 5Hz
b) Above 10Hz
c) Above 1 KHz
d) Very high frequency

Answer: a [Reason:] X-Y plotter is used for measuring phase difference between signals with very low frequencies. That is below 5Hz.

3. What is the expression for phase angle using X-Y plotter? (Assume t0 be time interval between zero crossing of signals and T be time period of signals.)
a) (360T0) ⁄ t0
b) (180 T0) ⁄ t0
c) (360 t0) ⁄ T0
d) (180 t0) ⁄ T0

Answer: c [Reason:] t0 is the time interval between zero crossing of two signals of the same frequency, and T0 is the time period of signals. Phase angle is represented by φ and is expressed in degree.

4. What is the use of flip-flop in electronic phase meters?
a) To provide a delay
b) To provide stability
c) To save data for particular time duration
d) To produce rectangular pulse

Answer: d [Reason:] Flip-flop in electronic phase meters are used to produce rectangular pulse with duration t which is equal to phase difference between signals.

5. Phase-Sensitive detectors are used for measuring phase of ______________.
a) Sinusoidal signals only
b) Non periodic signals only
c) Periodic signals only
d) Both periodic and non-periodic signals

Answers: c [Reason:] Phase sensitive detectors are used to measure phase and amplitude of periodic signals. It is done by comparing signal with a standard reference signal.

6. Rejection capability of Phase sensitive detector is depended on averaging time of smoothing filter.
a) True
b) False

Answer: a [Reason:] Rejection of noise signals in p.s.d is depended on averaging time of smoothing filter. Higher the averaging time, greater is its rejection capability.

7. For what purpose, FET’s are included in phase sensitive detectors?
a) As SPDT switches, for working with very high frequency signals
b) As SPDT switches, for working with very low frequency signals
c) As SPST switches, for working with very high frequency signals
d) As SPST switches, for working with very low frequency signals

Answer: b [Reason:] Field effect transistors are included as single-pole, double-throw switches to work with very low frequency signals.

8. Which of the following relation is correct for phase angle and reactive power?
a) Reactive power = apparent power ∗ sin θ
b) Reactive power = apparent power ⁄ sin θ
c) Reactive power = Real power ∗ sin θ
d) Reactive power = Real power ⁄ sin θ

Answer: a [Reason:] From the power triangle, using relation for sin function we obtain Reactive power is the product of apparent power and sin of phase angle.

9. Which of the following is the expression of power factor?
a) cos θ
b) sin θ
c) tan θ
d) sec θ

Answer: a [Reason:] Power factor is a measure of power usage of a system from total supplied power. It can be expressed as cos θ, in which θ represents phase angle.

10. What is the relation for phase angle (in degree) of a signal with time delay Δt and frequency f?
a) 3600∗f.∗ Δt
b) 1800∗f∗ Δt
c) 3600 ⁄ (f∗ Δt)
d) 1800 ⁄ (f∗ Δt)

Answer: a [Reason:] Phase angle of a signal in degree can be measured using the above formula, if frequency and time delay are known.

## Set 3

1. Photoelectric devices are sensitive to all wavelength.
a) True
b) False

Answer: b [Reason:] Photoelectric devices are sensitive to certain wavelength only hence they should be calibrated before every use.

2. In photo emissive transducers, electrons are attracted by ___________
a) Cathode
b) Anode
c) Grid
d) Body

Answer: b [Reason:] In photo emissive transducers, electrons emitted by cathode are attracted by anode plates.

3. Why inert gas is used in photo electric transducers?
a) To increase efficiency
b) To increase sensitivity
c) To increase robustness
d) None of the mentioned

Answer: b [Reason:] Inert gas of pressure 1mm Hg is filled in tube of photoelectric transducer to increase sensitivity.

4. Which of the following quantities are insensitive to solid state semiconductor photoelectric transducers?
a) X ray
b) Gamma ray
c) Alpha and beta rays
d) None of the mentioned

Answer: d [Reason:] Solid state photoelectric transducer made up of semiconductor are insensitive to X rays, gamma rays, alpha and beta rays etc.

5. LDR’s are also called_______________
a) Photo voltaic cell
b) Photo resistive cell
c) Photo emissive cell
d) All of the mentioned

Answer: b [Reason:] Photo resistive cells and LDR works on the interaction of light and its effect on resistance change.

6. Photo resistive cells are _____________
a) Active device
b) Passive device
c) Insulating device
d) None of the mentioned

Answer: b [Reason:] Passive devices are those doesn’t require external power source. Resistors and LDR’s are passive devices.

7. Which of the following materials can be used as photoconductive transducer?
a) Selenium
b) Silicon
c) Germanium
d) All of the mentioned

Answer: d [Reason:] Photoconductive cells are materials which changes conductivity on application of light.

8. Semiconductor layer using silicon and germanium is known as _______________
a) Photo diodes
b) Photo junction diodes
c) Photo material
d) Photo sensitive materials

Answer: b [Reason:] Photo junction diodes are semiconductor layers formed by silicon and germanium which are used in photovoltaic cells.

9. Which of the following are used to form photo transistors?
a) Two photo diodes
b) Three photo diodes
c) Normal diodes
d) None of the mentioned

Answer: a [Reason:] Photo transistors are formed by placing two photo diodes back to back.

10. Photo transistor is a three terminal device.
a) True
b) False

Answer: b [Reason:] Photo transistor contains only two terminals, which are collector and emitter. Base region is illuminated.

## Set 4

1. Which of the following is detected using manometer devices?
a) Pressure difference between manometric and measuring liquid
b) pH difference between manometric and measuring liquid
c) Density difference between manometric and measuring liquid
d) None of the mentioned

Answer: a [Reason:] In manometer devices pressure difference between manometric liquid and measuring liquid is obtained and it is equated to relation hϱg, ϱ is the mass density of manometric liquid.

2. What is the difference between water and transformer oil as manometric liquid?
a) Water is used for large pressure differential
b) Transformer oil is used for large pressure differential
c) Transformer oil has evaporation problems
d) Water has evaporation problems

Answer: d [Reason:] Both water and transformer oils are used in small pressure differential applications, but the difference is that water has problems related to relatively faster evaporation.

3. In which of the following categories be thin plate diaphragm included?
a) Primary transducer
b) Secondary transducer
c) Voltage measuring devices
d) Spring balance systems

Answer: a [Reason:]s: Primary transducers are devices which converts measurand into mechanical quantities. Diaphragm converts pressure into displacement which is a mechanical quantity.

4. Which of the following applications are suited for thin plate diaphragms?
a) Static pressure only
b) Dynamic pressure only
c) Both static and dynamic pressure with large frequency
d) Both static and dynamic pressure with small frequency

Answer: d [Reason:] Thin plate diaphragms can be used for measuring both static and dynamic pressures. But the limitation is that frequency of application should be small.

5. Using a membrane for measuring pressure, which of the following represents correct relation for displacement?
a) (R2 ΔP)/4S
b) ΔP/4S
c) (R2 ΔP)/S
d) (R2 ΔP)/2

Answer: a [Reason:] R is the radius of membrane and S is the radial tension in N/m. Displacement will be an indication of applied pressure.

6. Which of the following quantities can be measured using bellows?
a) Absolute pressure
b) Gauge pressure
c) Differential pressure
d) All of the mentioned

Answer: d [Reason:] Bellows can be used for measuring Absolute pressure, Gauge pressure and Differential pressure of measuring medium. This is accomplished using two bellow chambers provided.

7. Which of the following conversion take place in bourdon tubes?
a) Pressure to displacement
b) Pressure to voltage
c) Pressure to strain
d) Pressure to force

Answer: a [Reason:] In bourdon tubes converts input pressure into displacement and displacement of needle will be directly proportional to input pressure.

8. ‘Capsules are made from diaphragms’. Is this statement true or false?
a) True
b) False

Answer: a [Reason:] Capsules are made by enclosing two identical corrugated diaphragms forming a closed chamber.

9. ‘In bellows pressure to displacement conversion takes place’. Is this statement true or false?
a) True
b) False

Answer: b [Reason:] In bellows pressure to force conversion takes place, which is acted on bellows and can be measured for calculating applied pressure.

10. Which of the following devices convert pressure to displacement?
a) Diaphragm
b) Bellow
c) Capsule
d) Both diaphragm and capsule

Answer: d [Reason:] Both diaphragm and capsule converts pressure into displacement which can be measured using indicating instruments. Displacement will be proportional to applied pressure.

## Set 5

1.
Given a Wheatstone-bridge with external voltage V, Resistance Bridge with resistances P, Q, R, S, and galvanometer G. What is the balancing condition of bridge?
a) PQ=SR
b) PS=RQ
c) P = RQ
d) S = RQ

Answer: a [Reason:] A Wheatstone bridge is said to be balanced when galvanometer shows null deflection that is zero current flow through that path.

2. Who invented Wheatstone bridge?
a) Samuel Hunter Christie
b) Sir Charles Wheatstone
c) Joseph henry
d) Andrew Kay

Answer: a [Reason:] Wheatstone bridge was invented by Samuel Hunter in 1833, but it was improved and popularized by Charles Wheatstone in 1843.

3. In a Wheatstone bridge, which of the following is used as null detector?
a) Ammeter
b) Galvanometer
c) Voltmeter
d) Wattmeter

Answer: b [Reason:] Null detector is used to indicate zero current flow, and the device used is galvanometer.

4. Which of the following can be measured using a Wheatstone bridge?
a) Resistance only
b) Capacitance only
c) Inductance only
d) Resistance, capacitance, inductance, impedance

Answer: d [Reason:] Wheatstone bridge cannot be limited to measurement of a single quantity only, it can be used to measure resistance, capacitance, impedance, inductance etc. with some modifications.

5. Which of the following device is used for measuring low resistance value?
a) Wheatstone bridge
b) Hay bridge
c) Kelvin bridge
d) Owens bridge

Answer: c [Reason:] Kelvin Bridge is used for measuring very low resistance vales. Low resistance value is below 1Ω.

6. A null type instrument with DC excitation is _________________
a) Wheatstone bridge
b) Hay bridge
c) Anderson bridge
d) Wien bridge

Answer: a [Reason:] Wheatstone bridge is used for measuring resistance, which has a null detector circuit and external DC voltage.

7. Which of the following device is used with 4 terminal resistors?
a) Wheatstone bridge
b) Hay bridge
c) Wien bridge
d) Kelvin bridge

Answer: d [Reason:] Kelvin Bridge is used to work with 4 terminal resistances.

8. Why 4 terminal resistors are used?
a) For protection
b) To overcome parasitic resistances
c) To increase current flow
d) None of mentioned

Answer: b [Reason:] Four terminals in resistance are used for overcoming parasitic resistances.

9. What are the four terminals in four terminal resistance?
a) 3 current terminals and one voltage terminal
b) Two potential terminals and two current terminals
c) Four voltage terminals
d) Four current terminals