250+ TOP MCQs on Electrical Actuating Systems – Electrical Relays and Answers

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Mechatronics Multiple Choice Questions on “Electrical Actuating Systems – Electrical Relays”.

1. Who invented electrical relay?
a) Grueblerowen
b) Joseph Henry
c) Philip Vaughan
d) Robert Abalakov
Answer: b
Clarification: Joseph Henry invented electrical relay. He was an American scientist an electromagnetism pioneer who invented the electrical relay in the year 1835. This relay was made in order to improve the capabilities of electric telegraph.

2. What is the full form of MCB?
a) Miniature contact breaker
b) Mini circuit breaker
c) Miniature circuit breaker
d) Mini contact breaker
Answer: c
Clarification: MCB stands for miniature circuit breaker. It is an automatic electro mechanical switching device which is used in most of the houses, apartments, industries etc. This device automatically breaks the circuit from the main power supply when excessive current passes through it.

3. Which electrical relay contact tip material has the highest electrical conductivity?
a) Silver
b) Alloy of silver and copper
c) Alloy of silver and tungsten
d) Alloy of silver and Nickel
Answer: a
Clarification: Silver electrical relay contact tip has the highest electrical conductivity among the all mentioned above. The electrical as well as thermal conductivity of silver is much higher than any of its alloy.

4. Which type of relay can be used to automatically switch between transmitter and receiver configuration from a same antenna setup?
a) Mercury relay
b) Latching relay
c) Force-guided contacts relay
d) Coaxial relay
Answer: d
Clarification: Coaxial relay can be used to automatically switch between transmitter and receiver configuration from a same antenna setup. These relays are often used to perform switching action from receiver to transmitter and vice versa when only one antenna is present.

5. Solid state relays face high arching problems.
a) True
b) False
Answer: b
Clarification: Solid state relays do not face arching problems. Since solid state relays have no moving part therefore it does not face any arching problem. The arching problem of the ordinary electro mechanical relays was resolved by solid state relays.

6. Solid state relays have only one moving part which helps in switching between “ON” and “OFF” position.
a) True
b) False
Answer: b
Clarification: Solid state relays have no moving parts. The mechanical switching system in the primitive electro mechanical relays was replaced by power transistors, thyristors or triac’s. No physical movement takes place in solid state relays.

7. Which type of snubber network is required at the output terminal of the solid state relays to protect the semiconductor from transient spikes and unwanted noises?
a) RC (Resistor capacitor) type
b) RL (Resistor inductor) type
c) RLC (Resistor inductor capacitor) type
d) LC (Inductor capacitor) type
Answer: a
Clarification: RC (Resistor capacitor) type of snubber network is required at the output terminal of the solid state relays to protect the semiconductor from transient spikes and unwanted noises. Snubber circuits are those circuits which are used to suppress the voltage spikes.

8. Which type of solid state relay turns “ON” when a minimum operating control voltage is applied and the load voltage nearly reaches zero?
a) Instant ON Relays
b) Zero-Switching Relays
c) Peak Switching Relays
d) Analog Switching Relays
Answer: b
Clarification: Zero-Switching Relays turn “ON” when a minimum operating control voltage is applied and the load voltage nearly reaches zero. Zero switching relays wait for the alternating wave to reach zero for the relay to turn on.

9. Who developed the first Solid state relay?
a) Grueblerowen
b) Walcraft engineers
c) Crydom engineers
d) Robert Conrad
Answer: c
Clarification: Crydom engineers developed the first Solid state relay. These relays were developed in the year 1972. Solid state relays are switching device that can switch “ON” and “OFF” positions by a small input voltage.

10. Which is an example of relay?
a) KSD9700
b) XMPA06B2131
c) SLB700A/06VA
d) 792XDXM4L-24A
Answer: d
Clarification: 792XDXM4L-24A is an example of relay. It is manufactured by SCHNEIDER ELECTRIC /MAGNECRAFT. XMPA06B2131 is an example of pressure switch. KSD9700 is an example of temperature switch. SLB700A/06VA is an example of force sensor.

11. A good electrical relay contact tip should have higher arc resistance.
a) True
b) False
Answer: a
Clarification: A good electrical relay contact tip should have higher arc resistance. Too much arching or sparking can damage the contact tip. If the arching become severe, it can even weld the contact point which can led excess of current flow and can damage other components.

12. Relay and contactors perform different physical operation.
a) True
b) False
Answer: b
Clarification: Relay and contactors do not perform different physical operation. They have same physical operation. The only difference is the rated voltage on which they work. Contractors are relays that perform switching operation at high voltage. Whereas relays perform switching operation at low voltage.

13. Electro mechanical relay’s (EMR) needs to be manually turned “ON” and “OFF”.
a) True
b) False
Answer: a
Clarification: Electro mechanical relay’s (EMR) needs to be manually turned “ON” and “OFF”. This is one of the biggest disadvantages of Electro mechanical relay’s (EMR). Also they can only switch small electric current.

14. Which type of relay contains a glass tube which contains an inert gas which is used to protect the contacts from corrosion?
a) Polarised relay
b) Solid-state relay
c) Contactor
d) Reed relay
Answer: d
Clarification: Reed relays contain a glass tube which contains an inert gas which is used to protect the contacts from corrosion. These contacts move on the principle of magnetic effect of electric current. These contacts act as electromagnets which helps them to perform switching operation.

15. Which electrical relay contact tip material has the highest thermal conductivity?
a) Silver
b) Alloy of silver and copper
c) Alloy of silver and tungsten
d) Alloy of silver and Nickel
Answer: a
Clarification: Silver electrical relay contact tip has the highest thermal conductivity among the all mentioned above. The thermal as well as electrical conductivity of silver is much higher than any of its alloy.