Instrumentation Transducers

Measurement of Current

Question 1
Marks : +2 | -2
Pass Ratio : 100%
Which of the following can be treated as an equivalent of ampere?
Coulomb/second
Watt/second
Joule/second
Coulomb
Explanation:
Ampere can be treated as coulomb per second since it is the charge transferred in one second.
Question 2
Marks : +2 | -2
Pass Ratio : 100%
An induction meter can handle current up to __________
Below 10A
10A
50A
100A
Explanation:
Current handling capacity of induction meter is high up to 100A.
Question 3
Marks : +2 | -2
Pass Ratio : 100%
How many electrons are contributed in one coulomb electric charge?
6.242 × 1018
6.242 × 1019
6.242 × 1020
6.242 × 1010
Explanation:
Charge of one electron is 1.6 × 10-19coulumb, hence one coulomb implies reciprocal of 1.6×10-19 which is 6.25×1018.
Question 4
Marks : +2 | -2
Pass Ratio : 100%
What will be the average value of current, if its peak value is 43A?
27.4A
37.7A
21.5A
60.8A
Explanation:
Average current value is the product of peak value and 0.636.
Question 5
Marks : +2 | -2
Pass Ratio : 100%
Using a low resistant shunt Moving coil, permanent magnet instrument can be converted to ______________
Volt meter
Ammeter
Flux-meter
Watt meter
Explanation:
By applying a low resistant shunt in permanent magnet moving coil instrument can be converted to Ammeter.
Question 6
Marks : +2 | -2
Pass Ratio : 100%
Which of the following devices can be used with both AC and DC?
PMMC
Moving iron type
Moving coil type
Induction type
Explanation:
Moving iron type meters can be used in both AC and DC applications.
Question 7
Marks : +2 | -2
Pass Ratio : 100%
In a conductor after 1 minute of electron passage, current flown is found to be 1mA. How many electrons would have passed through that conductor?
4.5×1020
5×1017
3.75×1017
3.75×1018
Explanation:
For n number of electrons, total charge will be n×1.6×10-19. Then for charge passed in one second will be current flow, here 1mA.
Question 8
Marks : +2 | -2
Pass Ratio : 100%
Find the initial value of current for which transient current is given by
0
1
0.2
0.5
Explanation:
Initial value of current from transient response is found using initial value theorem on Laplace transform. Initial value theorem is given as
Question 9
Marks : +2 | -2
Pass Ratio : 100%
What is the purpose of making internal resistance of milli-ammeter very low?
High sensitivity
High accuracy
Minimum voltage drop across meter
Maximum voltage drop across meter
Explanation:
Low internal resistance will help in easy current flow. If we put a high resistance in series to current flow, it will cause large voltage drop to produce across meter.
Question 10
Marks : +2 | -2
Pass Ratio : 100%
Which of the following effect is used in AC ammeters?
Electromagnetic effect
Electrostatic effect
Chemical effect
Magnetic effect
Explanation:
AC ammeters use electromagnetic principle for operation. This effect is also employed in some integrating instruments.