39 + Interview Questions in Design Of Electromagnets in Design Of Electrical Machines Page 1 InterviewSolution

1.	What is the formula for the total winding area?(a) total winding area = number of turns * area of each conductor * space factor(b) total winding area = number of turns / area of each conductor * space factor(c) total winding area = number of turns * area of each conductor / space factor(d) total winding area = 1/number of turns * area of each conductor * space factorThe question was asked during a job interview.My question is taken from Design of Magnet Coils topic in division Design of Electromagnets of Design of Electrical Machines
Answer» Right option is (c) TOTAL WINDING area = number of turns * area of each CONDUCTOR / space factor For explanation: First the number of turns is CALCULATED along with the area of each conductor. Next, the space factor is calculated and on substitution gives the total winding area.

Discussion

2.	What is the formula for total number of turns in the magnet coils?(a) total number of turns = mmf per coil * current(b) total number of turns = mmf per coil / current(c) total number of turns = mmf per coil – current(d) total number of turns = mmf per coil + currentThis question was posed to me during an interview.Query is from Design of Magnet Coils topic in chapter Design of Electromagnets of Design of Electrical Machines
Answer» RIGHT choice is (b) total number of turns = mmf per coil / CURRENT Explanation: The mmf per coil is FIRST CALCULATED. Next, the current flowing through the COILS is measured and on substitution gives the total number of turns.

Discussion

3.	What is the value of the resistance temperature coefficient of copper?(a) 0.00393 per °C(b) 0.0040 per °C(c) 0.00383 per °C(d) 0.00373 per °CThe question was posed to me by my school teacher while I was bunking the class.The above asked question is from Design of Magnet Coils in chapter Design of Electromagnets of Design of Electrical Machines
Answer» The correct ANSWER is (a) 0.00393 per °C Explanation: The resistance TEMPERATURE COEFFICIENT of COPPER is CALCULATED at a temperature of 20°C. The resistance temperature coefficient of copper is 0.00393 per °C.

Discussion

4.	What is the formula for the area of the conductors of the magnet coils?(a) area of the conductors = mmf per coil * resistivity of conductor * length of mean turn * terminal voltage(b) area of the conductors = mmf per coil / resistivity of conductor * length of mean turn * terminal voltage(c) area of the conductors = mmf per coil * resistivity of conductor * length of mean turn / terminal voltage(d) area of the conductors = mmf per coil * resistivity of conductor / length of mean turn * terminal voltageThis question was posed to me during an interview.I want to ask this question from Design of Magnet Coils topic in section Design of Electromagnets of Design of Electrical Machines
Answer» RIGHT choice is (c) AREA of the conductors = mmf per coil * RESISTIVITY of CONDUCTOR * length of mean turn / terminal voltage The explanation: For calculating the area of the conductors, first the mmf per coil is CALCULATED along with the resistivity of conductors. The length of mean turn and terminal voltage is calculated and on substitution gives the area of the conductors.

Discussion

5.	What is the value of the resistivity temperature coefficient of copper?(a) 0.017 ohm per m per mm^2(b) 0.0173 ohm per m per mm^2(c) 0.01734 ohm per m per mm^2(d) 0.0175 ohm per m per mm^2I have been asked this question in homework.This intriguing question originated from Design of Magnet Coils in section Design of Electromagnets of Design of Electrical Machines
Answer» Correct option is (c) 0.01734 OHM PER m per mm^2 To elaborate: The resistivity temperature coefficient of COPPER is first CALCULATED at a temperature of 20°C. The resistivity temperature coefficient of copper is 0.01734 ohm per m per mm^2.

Discussion

6.	What is the ambient temperature of the magnet coils?(a) 10°C(b) 15°C(c) 20°C(d) 25°CThe question was asked in a national level competition.I'm obligated to ask this question of Design of Magnet Coils topic in chapter Design of Electromagnets of Design of Electrical Machines
Answer» The CORRECT choice is (c) 20°C The BEST I can explain: The temperature is ONE of the factors which is used in the efficient operation of the MAGNET coils. The AMBIENT temperature of the magnet coils is 20°C.

Discussion

7.	What is the formula of the inner cylindrical heat dissipating surface?(a) inner cylindrical heat dissipating surface = length of mean turn * axial length of coil(b) inner cylindrical heat dissipating surface = 2 length of mean turn axial length of coil(c) inner cylindrical heat dissipating surface = length of mean turn / axial length of coil(d) inner cylindrical heat dissipating surface =1 / length of mean turn * axial length of coilI had been asked this question in an interview for internship.Question is taken from Design of Magnet Coils in section Design of Electromagnets of Design of Electrical Machines
Answer» Correct choice is (b) inner CYLINDRICAL HEAT dissipating surface = 2 length of MEAN TURN axial length of coil Explanation: The length of mean turn is first calculated. NEXT, the axial length of coil is calculated and on substitution gives the inner cylindrical heat dissipating surface.

Discussion

8.	What is the formula for the outer cylindrical heat dissipating surface of the magnet coils?(a) outer cylindrical heat dissipating surface = 3.14 * outer diameter of coil + axial length of coil(b) outer cylindrical heat dissipating surface = 3.14 + outer diameter of coil + axial length of coil(c) outer cylindrical heat dissipating surface = 3.14 / outer diameter of coil + axial length of coil(d) outer cylindrical heat dissipating surface = 3.14 * outer diameter of coil * axial length of coilThe question was posed to me in final exam.My question is based upon Design of Magnet Coils in portion Design of Electromagnets of Design of Electrical Machines
Answer» Correct choice is (d) outer cylindrical heat dissipating SURFACE = 3.14 * outer diameter of coil * AXIAL length of coil To elaborate: The outer diameter of the coil is FIRST CALCULATED. Next, the axial length of the coil is next calculated and on substitution gives the outer cylindrical heat dissipating surface of the magnet coils.

Discussion

9.	What is the formula of the cross winding area of the magnet coils?(a) cross winding area = axial length of coil + depth of winding(b) cross winding area = axial length of coil – depth of winding(c) cross winding area = axial length of coil * depth of winding(d) cross winding area = axial length of coil / depth of windingI got this question in an interview for internship.I need to ask this question from Design of Magnet Coils topic in portion Design of Electromagnets of Design of Electrical Machines
Answer» Right option is (C) CROSS WINDING area = axial length of coil * depth of winding For explanation: First the axial length of coil is calculated. Next, the depth of winding is calculated and on SUBSTITUTION gives the cross winding area of the magnet COILS.

Discussion

10.	What is the formula for the total heat dissipating surface of the magnet coils?(a) total heat dissipating surface =length of mean turn * depth of winding * axial length of coil(b) total heat dissipating surface =length of mean turn * depth of winding + axial length of coil(c) total heat dissipating surface = 2 * length of mean turn * (depth of winding + axial length of coil)(d) total heat dissipating surface = 2 * length of mean turn * depth of winding * axial length of coilThis question was addressed to me during an interview.The doubt is from Design of Magnet Coils in division Design of Electromagnets of Design of Electrical Machines
Answer» Correct option is (C) TOTAL heat dissipating surface = 2 * length of mean turn * (DEPTH of winding + axial length of coil) For explanation I would say: The length of mean turn is calculated first. NEXT, the depth of winding and axial length of coil is next calculated and on SUBSTITUTION gives the total heat dissipating surface.

Discussion

11.	What is the formula for the length of mean turn of magnet coils?(a) length of mean turns = 3.14 * (inside diameter of coil + depth of windings)(b) length of mean turns = 3.14 / (inside diameter of coil + depth of windings)(c) length of mean turns = 3.14 * (inside diameter of coil * depth of windings)(d) length of mean turns = 3.14 + (inside diameter of coil + depth of windings)This question was addressed to me by my school principal while I was bunking the class.The query is from Design of Magnet Coils in section Design of Electromagnets of Design of Electrical Machines
Answer»

Discussion

12.	What materials are used along with paper for insulation?(a) varnish(b) glass(c) synthetic resin(d) varnish, glass, synthetic resinThe question was posed to me in an international level competition.This is a very interesting question from Construction of Electromagnets topic in division Design of Electromagnets of Design of Electrical Machines
Answer» Right ANSWER is (d) VARNISH, glass, synthetic resin To EXPLAIN: The insulation used in the electromagnets is paper. It is being INSULATED along with the varnish, glass and synthetic resin and treated into the form of sheets to form proper insulation.

Discussion

13.	What is the formula for depth of winding of the magnet coils?(a) depth of winding = mean diameter of coil – inner diameter(b) depth of winding = mean diameter of coil + inner diameter(c) depth of winding = mean diameter of coil – 2* inner diameter(d) depth of winding = mean diameter of coil + 2*inner diameterThis question was addressed to me in my homework.My query is from Design of Magnet Coils topic in division Design of Electromagnets of Design of Electrical Machines
Answer» Correct OPTION is (a) depth of winding = MEAN diameter of coil – inner diameter Easy explanation: The mean diameter of coil is calculated first from its respective formula. The inner diameter is NEXT calculated and on SUBSTITUTION gives the depth of winding.

Discussion

14.	What is the formula for the mean diameter of the magnet coils?(a) mean diameter = inside diameter of coil + outer diameter of coil / 2(b) mean diameter = inside diameter of coil – outer diameter of coil / 2(c) mean diameter = inside diameter of coil * outer diameter of coil / 2(d) mean diameter = inside diameter of coil / outer diameter of coil / 2This question was addressed to me in quiz.The origin of the question is Design of Magnet Coils topic in division Design of Electromagnets of Design of Electrical Machines
Answer» The CORRECT option is (a) mean diameter = INSIDE diameter of coil + OUTER diameter of coil / 2 Easy explanation: FIRST the inner diameter of coil is calculated. Secondly, the outer diameter of coil is calculated. On SUBSTITUTION, we finally get the mean diameter.

Discussion

15.	What is the formula for the outside diameter of the magnet coils?(a) outside diameter = mean diameter + 2depth of winding(b) outside diameter = mean diameter + depth of winding(c) outside diameter = mean diameter – 2depth of winding(d) outside diameter = mean diameter – depth of windingThe question was asked in an internship interview.This key question is from Design of Magnet Coils topic in chapter Design of Electromagnets of Design of Electrical Machines
Answer» Right answer is (b) outside diameter = MEAN diameter + DEPTH of WINDING For EXPLANATION: The mean diameter is found out from its respective formula. Next, the depth of the winding is calculated and on SUBSTITUTION gives the outside diameter.

Discussion

16.	The coil insulation used in the electromagnets is of sheet form.(a) true(b) falseThe question was posed to me by my college director while I was bunking the class.My question is taken from Construction of Electromagnets in portion Design of Electromagnets of Design of Electrical Machines
Answer» CORRECT CHOICE is (a) true To explain I would say: INSULATION material used in the machine is usually paper. The insulation is arranged in the FORM of SHEETS.

Discussion

17.	What is the conductor material being used in the electromagnet?(a) copper(b) zinc(c) bronze(d) aluminumThe question was posed to me in an interview for job.This intriguing question comes from Construction of Electromagnets in chapter Design of Electromagnets of Design of Electrical Machines
Answer» Correct CHOICE is (a) copper To elaborate: CONDUCTOR MATERIALS are being used in the electromagnet to CONDUCT the current in the electromagnet. Copper is the material used in the electromagnet.

Discussion

18.	What type of conductors are being used in the coils made of heavy wire?(a) circular(b) rounded(c) conical(d) rectangularI got this question in unit test.My question is based upon Construction of Electromagnets in division Design of Electromagnets of Design of Electrical Machines
Answer» The correct option is (d) rectangular To explain: The cross-section of coils is GENERALLY rectangular and the cross-section of CONDUCTORS is usually rounded. The coils made of HEAVY wires, rectangular conductors with rounded CORNERS are used.

Discussion

19.	Coils are being made use of in electromagnets as an exciting source for production of magnetic field.(a) true(b) falseThis question was addressed to me in quiz.Origin of the question is Construction of Electromagnets topic in division Design of Electromagnets of Design of Electrical Machines
Answer» Correct choice is (a) true The explanation: The coils are being made use of in ELECTROMAGNETS. They are USED as an EXCITING source for the production of MAGNETIC field.

Discussion

20.	What is the insulation material being used in the electromagnets?(a) paper(b) wood(c) brass(d) copperThis question was addressed to me during an interview.This intriguing question originated from Construction of Electromagnets topic in portion Design of Electromagnets of Design of Electrical Machines
Answer» Correct answer is (a) paper To EXPLAIN I WOULD say: INSULATION material is being used in between the coils of the ELECTROMAGNET to provide insulation. The material used in the electromagnet is paper.

Discussion

21.	What are the non-magnetic materials being used in the electromagnets?(a) silicon(b) molybdenum(c) silicon, chromium, molybdenum(d) chromiumThe question was asked in quiz.The question is from Construction of Electromagnets in division Design of Electromagnets of Design of Electrical Machines
Answer» Right choice is (c) SILICON, chromium, molybdenum Best explanation: The ELECTROMAGNETS CONSISTS of the FERROMAGNETIC core. Some times the non-ferro-magnetic MATERIALS are being made use of like silicon, chromium and molybdenum.

Discussion

22.	What type of core does the electromagnetic consist of?(a) paramagnetic(b) diamagnetic(c) ferromagnetic(d) paramagnetic and diamagneticI had been asked this question during a job interview.The query is from Construction of Electromagnets topic in division Design of Electromagnets of Design of Electrical Machines
Answer» Right OPTION is (c) ferromagnetic The explanation is: Electromagnets consists of a ferromagnetic core. It carries the flux and a WINDING which produces a flux when excited by an EXTERNAL SOURCE.

Discussion

23.	What are the ferromagnetic elements used in the electromagnets?(a) iron(b) nickel(c) cobalt(d) iron, nickel, cobaltI got this question in quiz.Query is from Construction of Electromagnets in chapter Design of Electromagnets of Design of Electrical Machines
Answer»

Discussion

24.	What material is used for the construction of core of electromagnets?(a) soft magnetic materials(b) hard magnetic materials(c) non-magnetic materials(d) anti-ferromagnetic materialsI had been asked this question in class test.Query is from Construction of Electromagnets topic in chapter Design of Electromagnets of Design of Electrical Machines
Answer» RIGHT option is (a) soft magnetic materials Best explanation: The electromagnets consist of FERROMAGNETIC core. The soft magnetic materials are made USE of in the CONSTRUCTION of core of electromagnets.

Discussion

25.	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 lengthI have been asked this question during an online exam.The doubt is from Types of Electromagnets topic in portion Design of Electromagnets of Design of Electrical Machines
Answer» Right option is (C) force is directly proportional to the square of the AIR gap length 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.

Discussion

26.	Horse shoe is usually employed for the small magnets.(a) true(b) falseI got this question in exam.Question is from Types of Electromagnets in chapter Design of Electromagnets of Design of Electrical Machines
Answer» Correct choice is (a) true 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.

Discussion

27.	How many air gaps are present in the flat-faced plunger type?(a) 1(b) 2(c) 3(d) 4This question was posed to me during a job interview.I'd like to ask this question from Types of Electromagnets topic in portion Design of Electromagnets of Design of Electrical Machines
Answer» Correct OPTION is (a) 1 The best I can explain: The magnetic CIRCUIT in the FLAT faced plunger type is usually SHORT and heavy. It has only one air GAP present.

Discussion

28.	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 lengthThe question was asked in an international level competition.I'm obligated to ask this question of Types of Electromagnets in division Design of Electromagnets of Design of Electrical Machines
Answer» Right choice is (c) force is directly proportional to the square of the air gap LENGTH Easy 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.

Discussion

29.	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 seriesThis question was addressed to me during a job interview.Question is taken from Types of Electromagnets topic in division Design of Electromagnets of Design of Electrical Machines
Answer» Right option is (a) magnetic in series and mechanical in parallel The 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.

Discussion

30.	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 chucksThis question was addressed to me in an international level competition.Enquiry is from Types of Electromagnets in portion Design of Electromagnets of Design of Electrical Machines
Answer»

Discussion

31.	What material is the flat faced armature type made of?(a) hard steel(b) cast steel(c) cast iron(d) soft steelThe question was posed to me in quiz.My doubt stems from Types of Electromagnets in division Design of Electromagnets of Design of Electrical Machines
Answer» The correct ANSWER is (b) CAST STEEL To explain: The flat faced armature type is made up of cast steel. It is used for lifting SCRAP iron, sheet iron and iron castings.

Discussion

32.	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 supplyI had been asked this question in a national level competition.I would like to ask this question from Types of Electromagnets in section Design of Electromagnets of Design of Electrical Machines
Answer» Right option is (b) only DC supply Easy explanation: Portative electromagnets are ONE type of ELECTROMAGNET, which function as a HOLDING magnet. They operated usually from dc supply only.

Discussion

33.	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 typeThis question was addressed to me in semester exam.This key question is from Types of Electromagnets topic in portion Design of Electromagnets of Design of Electrical Machines
Answer» The correct option is (a) flat-faced armature TYPE 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.

Discussion

34.	How many most commonly used electromagnets are present?(a) 2(b) 3(c) 4(d) 5This question was addressed to me during an online interview.I would like to ask this question from Types of Electromagnets in division Design of Electromagnets of Design of Electrical Machines
Answer» RIGHT OPTION is (b) 3 To elaborate: 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.

Discussion

35.	How does the portative electromagnet work as?(a) holding magnet(b) connecting magnet(c) repulsion magnets(d) attraction magnetsThe question was asked in an online interview.I'm obligated to ask this question of Types of Electromagnets in section Design of Electromagnets of Design of Electrical Machines
Answer» Right ANSWER is (a) holding magnet Easiest EXPLANATION: The second TYPE of electromagnet is the portative electromagnet. They USUALLY function as a holding magnet.

Discussion

36.	Among the following what are the applications of the tractive electromagents?(a) track switches(b) electric bells(c) buzzers(d) track switches, bells, buzzersI had been asked this question in final exam.The above asked question is from Types of Electromagnets topic in portion Design of Electromagnets of Design of Electrical Machines
Answer» Right OPTION is (d) track switches, BELLS, buzzers Easy EXPLANATION: The tractive ELECTROMAGNETS have a large number of applications. They are made use of in the track switches, electric bells and buzzers.

Discussion

37.	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 supplyI have been asked this question in an online interview.This intriguing question comes from Types of Electromagnets in section Design of Electromagnets of Design of Electrical Machines
Answer» The correct OPTION is (d) ac or dc supply Easy explanation: The other name for the tractive electromagnet is SOLENOIDS. The tractive ELECTROMAGNETS are OPERATED either from ac or dc supply.

Discussion

38.	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 movementThis question was addressed to me in an online interview.My question is taken from Types of Electromagnets in division Design of Electromagnets of Design of Electrical Machines
Answer» The CORRECT option is (b) solenoidal, MECHANICAL movement The best explanation: The other name for the tractive electromagnet is SOLENOIDS. They are designed to PRODUCE mechanical.

Discussion

39.	How many types of electromagnets are present?(a) 2(b) 3(c) 4(d) 5The question was asked during a job interview.My question is from Types of Electromagnets in portion Design of Electromagnets of Design of Electrical Machines
Answer» Right CHOICE is (a) 2 Easy explanation: There are 2 types of ELECTROMAGNETS PRESENT. They are i) Tractive type and ii) Portative type.

Discussion

Explore topic-wise InterviewSolutions in .

What is the ambient temperature of the magnet coils?(a) 10°C(b) 15°C(c) 20°C(d) 25°CThe question was asked in a national level competition.I'm obligated to ask this question of Design of Magnet Coils topic in chapter Design of Electromagnets of Design of Electrical Machines

The coil insulation used in the electromagnets is of sheet form.(a) true(b) falseThe question was posed to me by my college director while I was bunking the class.My question is taken from Construction of Electromagnets in portion Design of Electromagnets of Design of Electrical Machines

What is the conductor material being used in the electromagnet?(a) copper(b) zinc(c) bronze(d) aluminumThe question was posed to me in an interview for job.This intriguing question comes from Construction of Electromagnets in chapter Design of Electromagnets of Design of Electrical Machines

What type of conductors are being used in the coils made of heavy wire?(a) circular(b) rounded(c) conical(d) rectangularI got this question in unit test.My question is based upon Construction of Electromagnets in division Design of Electromagnets of Design of Electrical Machines

Coils are being made use of in electromagnets as an exciting source for production of magnetic field.(a) true(b) falseThis question was addressed to me in quiz.Origin of the question is Construction of Electromagnets topic in division Design of Electromagnets of Design of Electrical Machines

What are the non-magnetic materials being used in the electromagnets?(a) silicon(b) molybdenum(c) silicon, chromium, molybdenum(d) chromiumThe question was asked in quiz.The question is from Construction of Electromagnets in division Design of Electromagnets of Design of Electrical Machines

What are the ferromagnetic elements used in the electromagnets?(a) iron(b) nickel(c) cobalt(d) iron, nickel, cobaltI got this question in quiz.Query is from Construction of Electromagnets in chapter Design of Electromagnets of Design of Electrical Machines

Horse shoe is usually employed for the small magnets.(a) true(b) falseI got this question in exam.Question is from Types of Electromagnets in chapter Design of Electromagnets of Design of Electrical Machines

How many air gaps are present in the flat-faced plunger type?(a) 1(b) 2(c) 3(d) 4This question was posed to me during a job interview.I'd like to ask this question from Types of Electromagnets topic in portion Design of Electromagnets of Design of Electrical Machines

What material is the flat faced armature type made of?(a) hard steel(b) cast steel(c) cast iron(d) soft steelThe question was posed to me in quiz.My doubt stems from Types of Electromagnets in division Design of Electromagnets of Design of Electrical Machines

How many most commonly used electromagnets are present?(a) 2(b) 3(c) 4(d) 5This question was addressed to me during an online interview.I would like to ask this question from Types of Electromagnets in division Design of Electromagnets of Design of Electrical Machines

How many types of electromagnets are present?(a) 2(b) 3(c) 4(d) 5The question was asked during a job interview.My question is from Types of Electromagnets in portion Design of Electromagnets of Design of Electrical Machines