This set of Design of Electrical Machines Multiple Choice Questions & Answers (MCQs) focuses on “Types of Electromagnets”.
1. How many types of electromagnets are present?
a) 2
b) 3
c) 4
d) 5
View Answer
Explanation: There are 2 types of electromagnets present. They are i) Tractive type and ii) Portative type.
2. What is the other name of the Tractive electromagnet and what is the means of movement of the armature?
a) solenoidal, electrical movement
b) solenoidal, mechanical movement
c) traction, electrical movement
d) traction, mechanical movement
View Answer
Explanation: The other name for the tractive electromagnet is solenoids. They are designed to produce mechanical.
3. What is the supply given to the tractive electromagnets?
a) only dc supply
b) only ac supply
c) ac and dc supply
d) ac or dc supply
View Answer
Explanation: The other name for the tractive electromagnet is solenoids. The tractive electromagnets are operated either from ac or dc supply.
4. Among the following what are the applications of the tractive electromagents?
a) track switches
b) electric bells
c) buzzers
d) track switches, bells, buzzers
View Answer
Explanation: The tractive electromagnets have a large number of applications. They are made use of in the track switches, electric bells and buzzers.
5. How does the portative electromagnet work as?
a) holding magnet
b) connecting magnet
c) repulsion magnets
d) attraction magnets
View Answer
Explanation: The second type of electromagnet is the portative electromagnet. They usually function as a holding magnet.
6. What type of supply is being provided to the portative electromagnet?
a) only ac supply
b) only dc supply
c) ac and dc supply
d) ac or dc supply
View Answer
Explanation: Portative electromagnets are one type of electromagnet, which function as a holding magnet. They operated usually from dc supply only.
7. How many most commonly used electromagnets are present?
a) 2
b) 3
c) 4
d) 5
View Answer
Explanation: There are 3 most commonly used electromagnets are present. They are I) Flat-faced armature type, II) Horse shoe type, III) Flat-faced plunger type.
8. What type of magnet is made use of to produce large force through a relatively small distance?
a) flat-faced armature type
b) horse shoe type
c) flat-faced plunger type
d) flat-faced plunger type and horse shoe type
View Answer
Explanation: There are 3 types of most commonly used electromagnets. The flat faced armature type electromagnet is made use of to produce large force through a relatively small distance.
9. What material is the flat faced armature type made of?
a) hard steel
b) cast steel
c) cast iron
d) soft steel
View Answer
Explanation: The flat faced armature type is made up of cast steel. It is used for lifting scrap iron, sheet iron and iron castings.
10. How are the air gaps arranged in the flat faced armature type?
a) magnetic in series and mechanical in parallel
b) magnetic in series and parallel
c) mechanical in series and parallel
d) magnetic in parallel and mechanical in series
View Answer
Explanation: The flat faced armature types have 2 air gaps within them. They are magnetic in series and are mechanical in parallel and hence produce a holding surface of large effective area.
11. Which among the following are the application of portative electromagnets?
a) lifting magnets
b) magnetic clutches
c) magnetic chucks
d) lifting magnets, magnetic clutches, magnetic chucks
View Answer
Explanation: The portative electromagnets generally function as holding magnets. The lifting magnets, magnetic chucks, magnetic clutches are all applications of portative electromagnets.
12. What is the relation between force and the air gap length in the flat-faced armature type?
a) force is directly proportional to the air gap length
b) force is indirectly proportional to the air gap length
c) force is directly proportional to the square of the air gap length
d) force is indirectly proportional to the square of the air gap length
View Answer
Explanation: The force is directly proportional to the square of the air gap length. This condition exists under ideal conditions wherein the effects of saturation and magnetic leakage are negligible.
13. Horse shoe is usually employed for the small magnets.
a) true
b) false
View Answer
Explanation: The horse shoe is usually employed for the small magnets. It is because of the mechanical adaptability and the ease with which it can be constructed.
14. How many air gaps are present in the flat-faced plunger type?
a) 1
b) 2
c) 3
d) 4
View Answer
Explanation: The magnetic circuit in the flat faced plunger type is usually short and heavy. It has only one air gap present.
15. What is the relation of the force and the air gap length in the flat faced plunger type?
a) force is directly proportional to the air gap length
b) force is indirectly proportional to the air gap length
c) force is directly proportional to the square of the air gap length
d) force is indirectly proportional to the square of the air gap length
View Answer
Explanation: Force is directly proportional to the square of the air gap length. The characteristics are similar to that of the flat-faced armature type.
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