1. The use of ........... instruments are merely confined within laboratories as standardizing instruments.
A. Absolute
B. Indicating
C. Recording
D. Integrating
E. None of the above
Answer: A. Absolute
Explanation:
Absolute Instruments:
- These instruments give the magnitude of the quantity under measurements in terms of physical constants of the instrument
- There is no necessity of calibrating or comparing with other instruments
- Tangent Galvanometer and Rayleigh’s current balance are example of this class
Secondary Instruments:
- These instruments are so constructed that the quantity being measured can only be measured by observing the output indicated by the instrument
- These instruments are calibrated by comparison with an absolute instrument or any other secondary instrument which has already been calibrated against an absolute instrument
- A voltmeter, a glass thermometer and a pressure gauge are typical examples of secondary instruments
- Working with absolute instruments for routine work is time consuming.
- Therefore, secondary instruments are most commonly used.
- Absolute instruments are seldom used except in standard institutions and laboratories while secondary instruments find usage almost in every sphere of measurement.
2. Which of the following instruments indicate the instantaneous value of the electrical quantity being measured at the time at which it is being measured?
A. Absolute instruments
B. Indicating instruments
C. Recording instruments
D. Integrating instruments
Answer: B. Indicating instruments
Explanation:
Indicating Instruments:
- These indicates the quantity being measured by means of a pointer which moves on a scale.
- These instruments indicate the instantaneous value of the electrical quantity being measured at the time at which it is being measured.
- Example: Ammeter, Voltmeter, Wattmeter
Recording Instruments:
- These instruments record continuously the variation of any electrical quantity with respect to time.
- In principle, these are indicating instruments but so arranged that a permanent continuous record of the indication is made on a chart or dial.
- Any electrical quantity like current, voltage can be recorded by a suitable recording mechanism.
- Example: A potentiometric type of recorder used for monitoring temperature records the instantaneous temperatures on a strip chart recorder.
Integrating Instruments:
- These instruments record the consumption of the total quantity of electricity, energy etc. during a particular period of time.
- These instruments give reading for a specific period of time but no indication of reading for a particular instant of time.
- Example: Ampere-hour meter, Energy meter, kilovolt ampere hour meter.
3. ......... instruments are those which measure the total quantity of electricity delivered in a particular time.
A. Absolute
B. Indicating
C. Recording
D. Integrating
Answer: D. Integrating
Explanation:
Integrating Instruments:
- These instruments record the consumption of the total quantity of electricity, energy, etc. during a particular period of time. These instruments give reading for a specific period of time but no indication of reading for a particular instant of time.
- Example: Ampere-hour meter, Energy meter, kilovolt ampere-hour meter.
Indicating Instruments:
- These indicates the quantity being measured by means of a pointer which moves on a scale.
- These instruments indicate the instantaneous value of the electrical quantity being measured at the time at which it is being measured.
- Example: Ammeter, Voltmeter, Wattmeter
Recording Instruments:
- These instruments record continuously the variation of any electrical quantity with respect to time.
- In principle, these are indicating instruments but so arranged that a permanent continuous record of the indication is made on a chart or dial.
- Any electrical quantity like current, voltage can be recorded by a suitable recording mechanism.
- Example: A potentiometric type of recorder used for monitoring temperature records the instantaneous temperatures on a strip chart recorder.
4. Which of the following are integrating instruments?
A. Ammeters
B. Voltmeters
C. Wattmeter's
D. Ampere-hour and watt-hour meters
Answer: D. Ampere-hour and watt-hour meters
Explanation:
Integrating Instruments:
- These instruments record the consumption of the total quantity of electricity, energy, etc. during a particular period of time. These instruments give reading for a specific period of time but no indication of reading for a particular instant of time.
- Integrating instruments totalize events over a specified period of time. The summation, which they give is the product of time and electrical quantity. Ampere hour and watt hour (energy) meters are examples of this category.
- Example: Ampere-hour meter, Energy meter, kilovolt ampere-hour meter.
5. Resistances can be measured with the help of
A. wattmeter
B. voltmeters
C. ammeters
D. ohmmeters and resistance bridges
E. all of the above
Answer: D. ohmmeters and resistance bridges
Explanation:
- Resistance is measured using an instrument such as an analog multimeter or digital multimeter.
- Both types of instruments can measure not only resistance, but also current, voltage, and other parameters, so they can be used in a variety of situations.
Device | Quantity to be Measured |
Ammeters | current |
Voltmeters | Voltage |
Wattmeter’s | Power |
Ohmmeters and resistance bridges | Resistance |
6 According to application, instruments are classified as
A. switch board
B. portable
C. both A and B
D. moving coil
E. moving iron
F. both D and E
Answer: C. both A and B
Explanation:
According to the application, instruments are classified into types.
Switch board and Panel Instruments:
- Measuring instruments for switchboards have a square or a rectangular front
- The pointers and scales for these instruments should be so that the position of the pointer is conspicuous, the scale markings are legible and there is a contrast with the background
- Pointers are usually broad or carry broad targets as their ends
- Aluminum strip or tube is used for making pointers
- The scale is generally printed on the enameled surface of a metal plate or on paper or cardboard pasted to a metal plate
- These types of instruments should be mounted in a vertical position.
Portable Instruments:
- These usually have knife-edge pointer moving over scale marked with fine lines
- If the pointer and scale are in different planes, observational errors may result on account of parallax
- These parallax errors can be avoided by using knife-edge pointers and scales mounted in the same plane as a tip of the pointer
7. Which of the following essential features is possessed by an indicating instrument?
A. Deflecting device
B. Controlling device
C. Damping device
D. All of the above
Answer: D. All of the above
Explanation:
The essential features are possessed by an indicating instrument deflecting, controlling and a damping device.
Deflecting device:
- Deflection device produces deflecting torque which causes the moving system to move from its zero position.
Controlling device:
- Controlling device produce the controlling torque (Tc) which opposes the deflecting torque and increases with the deflection of the moving system.
- It also brings the pointer back to zero when the deflecting torque is removed.
Damping device:
- This device produces damping torque this torque is necessary to bring the pointer to rest quickly.
- This damping torque (Td) acts only when the pointer is in motion and always opposes the motion
8. A device prevents the oscillation of the moving system and enables the larger to reach its final position quickly
A. deflecting
B. controlling
C. damping
D. any of the above
Answer: C. damping
Explanation:
- A 'damping' device prevents the oscillation of the moving system and enables the latter to reach its final position quickly.
- Ex: - sound-proofing technology dampens the oscillations of sound waves.
- Damping devices can operate mechano -hydraulically as throttle valves or bypass valves or electro-mechanically.
- It is a mechanical device designed to dissipate kinetic energy.
9. The spring material used in a spring control device should have the following Property
A. Should be non-magnetic
B. Most be of low temperature coefficient
C. Should have low specific resistance
D. Should not be subjected to fatigue
E. All of the above
Answer: E. All of the above
Explanation:
The essential requirements for instrument for instrument springs are:
- They should be non-magnetic
- They should be proof from mechanical fatigue
- Where springs are used to lead current into moving system they should have a small resistance, their cross-sectional area must be sufficient to carry the current without temperature rise affecting their constant.
- They should also have a low resistance temperature coefficient.
For most applications phosphor bronze has been found to be the most suitable material except in instruments low in resistance (like multi-voltmeters).
10. Which of the following properties a damping oil must possess?
A. Must be a good insulator
B. Should be non-evaporating
C. Should not have corrosive action upon the metal of the vane
D. The viscosity of the oil should not change with the temperature
E. all of the above
Answer: E. all of the above
Explanation:
Damping oil must have:
- Should be non-evaporating
- Should not have corrosive action upon the metal of the vane
- The viscosity of the oil should not change with the temperature
- Must be good insulator