Mechatronics Questions and Answers – Electrical Power Supply and Protection

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This set of Mechatronics Multiple Choice Questions & Answers (MCQs) focuses on “Electrical Power Supply and Protection”.

1. What is the medium in which arc is kept in SF6 circuit breaker?
a) Oil
b) Air
c) Sand
d) Sulphur hexafluoride
View Answer

Answer: d
Explanation: Arc of SF6 circuit breaker is kept in Sulphur hexafluoride medium. The in Sulphur hexafluoride present in it acts as very good arch quenching media and also acts as insulating medium for breaking the circuits in SF6 type circuit breakers.
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2. SF6 circuit breakers are better than BOCB (Bulk oil circuit breaker).
a) True
b) False
View Answer

Answer: a
Explanation: SF6 circuit breakers are better than BOCB (Bulk oil circuit breaker). It is so because SF6 circuit breaker uses Sulphur hexafluoride inside the setup which has very good arch quenching property along with highly favourable physical and chemical properties.

3. Which is not a property of Sulphur hexafluoride?
a) Colourless
b) Odourless
c) Toxic
d) Non-Inflammable
View Answer

Answer: c
Explanation: Sulphur hexafluoride is a Non-toxic gas. It has no colour and it also has no distinguishing smell. It is inflammable along with excellent arc quenching properties. It is used in SF6 type circuit breakers.
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4. What is the dielectric strength of Sulphur hexafluoride used in SF6 type circuit breaker?
a) 2.5 times of air
b) 2.5 times of water
c) 2.5 times of oil
d) 2.5 times of glass
View Answer

Answer: a
Explanation: The dielectric strength of Sulphur hexafluoride used in SF6 type circuit breaker is 2.5 times that of air. Sulphur hexafluoride has excellent physical, chemical and arc quenching properties. Also it acts as very good insulator that is why it is used in the SF6 type circuit breakers.

5. Potential difference and EMF (Electro-motive force) are same.
a) True
b) False
View Answer

Answer: b
Explanation: Potential difference and EMF (Electro-motive force) are not same. They are different in many aspects such as EMF (Electro-motive force) is independent of resistance but the potential difference depends on resistance.
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6. What does “MCB” stand for?
a) Miniature circuit breaker
b) Mini circuit breaker
c) Miniature capacitor breaker
d) Mini Capacitance breaker
View Answer

Answer: a
Explanation: “MCB” stands for Miniature circuit breaker. It works on magnetic effect of electric current. When there is overflow of electric current, it creates a magnetic field that repels the magnet present in the switch. This repulsion breaks the circuit and restricts the flow of current.

7. What is the principal on which MCB (Miniature circuit breaker) works ?
a) Magnetic effect of electric current
b) Lenz law
c) Faradays law of electric current
d) Flemings Right hand rule
View Answer

Answer: a
Explanation: MCB (Miniature circuit breaker) works on magnetic effect of electric current. When there is overflow of electric current, it creates a magnetic field that repels the magnet present in the switch. This repulsion breaks the circuit and restricts the flow of current.
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8. What is the medium in which arc is kept in BOCB (Bulk oil circuit breaker)?
a) Oil
b) Air
c) Sand
d) Water
View Answer

Answer: a
Explanation: Arc of BOCB (Bulk oil circuit breaker) is kept in oil medium. The oil present in it acts as a arch quenching media and also acts as a insulating medium for breaking the circuits in bulk oil type circuit breakers.

9. Which material is commonly used for making the arch of circuit breakers?
a) Copper
b) Tungsten
c) Aluminium
d) Copper tungsten alloy
View Answer

Answer: d
Explanation: Copper tungsten alloy is commonly used for making the arch of circuit breakers. Tungsten has an advantage that it has a very high level temperature resistance, whereas copper provides an excellent conducting property.
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10. What does “BOCB” stand for in context to circuit protections?
a) Bulk on-spot circuit breakers
b) Bonded oil circuit breaker
c) Bulk oiled circuit breaker
d) Bulk oil circuit breaker
View Answer

Answer:d
Explanation: “BOCB” stands for Bulk oil circuit breaker in context to circuit protections. In these types of circuit breaker, oil acts as an insulating medium that interrupts the flow of current during the time of short circuits.

11. What is the standard colour of ac supply ground wire in India?
a) Red
b) Magenta
c) Pink
d) Green
View Answer

Answer: d
Explanation: The standard colour of ac supply ground wire in India is green. Separate standard colours are assigned for wires carrying AC (Alternating current) supply which comes in our homes in order to easily understand the significance of each wires.

12. What is the standard colour of ac supply live wire in India?
a) Red
b) Magenta
c) Pink
d) Green
View Answer

Answer: a
Explanation: The standard colour of ac supply live wire in India is Red. Separate standard colours are assigned for wires carrying AC (Alternating current) supply which comes in our homes in order to easily understand the significance of each wires.

13. What is the standard colour of ac supply neutral wire in India?
a) Red
b) Black
c) Pink
d) Green
View Answer

Answer: b
Explanation: The standard colour of ac supply neutral wire in India is Black. Separate standard colours are assigned for wires carrying AC (Alternating current) supply which comes in our homes in order to easily understand the significance of each wires.

14. Green and yellow striped wire is also used to indicate ac (alternating current) supply live wire.
a) True
b) False
View Answer

Answer: b
Explanation: Green and yellow striped wire is also not used to indicate 220 volt ac(alternating current) supply live wire. It is used to denote ground wire of an ac (alternating current) supply. It is also called as earthing wire.

15. Live wire and hot wire are same.
a) True
b) False
View Answer

Answer: a
Explanation: Live wire and hot wire are same. Live wires are sometimes also referred as hot wires which carry’s the supply voltage. In India red colour is assigned for the indication of AC (alternating current) live wire.

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Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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