Current Measurement - Instrumentation Transducers Questions and Answers

This set of Instrumentation Transducers Multiple Choice Questions & Answers (MCQs) focuses on “Measurement of Current”.

1. Find the initial value of current for which transient current is given by
I(S) = ^(S²+S)⁄_(5S²+1)
a) 0
b) 1
c) 0.2
d) 0.5
View Answer

Answer: c
Explanation: Initial value of current from transient response is found using initial value theorem on Laplace transform. Initial value theorem is given as
^Lt_t→0x(t)=^Lt_s→∞S.X(S).

2. What is the purpose of making internal resistance of milli-ammeter very low?
a) High sensitivity
b) High accuracy
c) Minimum voltage drop across meter
d) Maximum voltage drop across meter
View Answer

Answer: c
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.

3. Which of the following devices can be used with both AC and DC?
a) PMMC
b) Moving iron type
c) Moving coil type
d) Induction type
View Answer

Answer: b
Explanation: Moving iron type meters can be used in both AC and DC applications.

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4. How many electrons are contributed in one coulomb electric charge?
a) 6.242 × 10¹⁸
b) 6.242 × 10¹⁹
c) 6.242 × 10²⁰
d) 6.242 × 10¹⁰
View Answer

Answer: a
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.

5. 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?
a) 4.5×10²⁰
b) 5×10¹⁷
c) 3.75×10¹⁷
d) 3.75×10¹⁸
View Answer

Answer: c
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.

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6. Which of the following can be treated as an equivalent of ampere?
a) Coulomb/second
b) Watt/second
c) Joule/second
d) Coulomb
View Answer

Answer: a
Explanation: Ampere can be treated as coulomb per second since it is the charge transferred in one second.

7. What will be the average value of current, if its peak value is 43A?
a) 27.4A
b) 37.7A
c) 21.5A
d) 60.8A
View Answer

Answer: a
Explanation: Average current value is the product of peak value and 0.636.

8. Using a low resistant shunt Moving coil, permanent magnet instrument can be converted to ______________
a) Volt meter
b) Ammeter
c) Flux-meter
d) Watt meter
View Answer

Answer: b
Explanation: By applying a low resistant shunt in permanent magnet moving coil instrument can be converted to Ammeter.

9. An induction meter can handle current up to __________
a) Below 10A
b) 10A
c) 50A
d) 100A
View Answer

Answer: d
Explanation: Current handling capacity of induction meter is high up to 100A.

10. Which of the following effect is used in AC ammeters?
a) Electromagnetic effect
b) Electrostatic effect
c) Chemical effect
d) Magnetic effect
View Answer

Answer: a
Explanation: AC ammeters use electromagnetic principle for operation. This effect is also employed in some integrating instruments.

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