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51.

The emf induced in a coil having N turns is?(a) e=ϕ/t(b) e=N*ϕ/t(c) e=N*ϕ*t(d) e=N^2*ϕ*tThe question was posed to me in quiz.My question comes from Magnitude of the Generated or Induced EMF topic in portion Electromagnetism of Basic Electrical Engineering

Answer»

Correct answer is (B) e=N*ϕ/t

Easy EXPLANATION: The emf induced in a COIL having N turns is, e=N*ϕ/t. This is because, the emf in a SINGLE coil is the flux linkage PER unit time, that is, phi/t. Hence the flux induced in N turns is N*ϕ/t.
Discussion
52.

The relation between the direction of magnetic flux and the direction of motion of the conductor is _______(a) Parallel(b) Equal(c) Not related(d) PerpendicularI had been asked this question in an online interview.Enquiry is from Direction of Induced EMF topic in division Electromagnetism of Basic Electrical Engineering

Answer» RIGHT option is (d) Perpendicular

For explanation I would SAY: According to FLEMING’s right HAND rule, the induced EMF, the motion of the conductor and the magnetic flux are mutually perpendicular.
Discussion
53.

The relation between the direction of induced emf and the direction of magnetic flux is _______(a) Parallel(b) Equal(c) Not related(d) PerpendicularI have been asked this question in exam.Question is from Direction of Induced EMF topic in division Electromagnetism of Basic Electrical Engineering

Answer»

The correct option is (d) Perpendicular

Easiest explanation: According to FLEMING’s RIGHT hand rule, the induced EMF, the motion of the CONDUCTOR and the magnetic flux are MUTUALLY perpendicular.
Discussion
54.

Direction of induced emf is determined by __________(a) Fleming’s left hand rule(b) Fleming’s right hand rule(c) Faraday’s law(d) Right hand thumb ruleThe question was asked by my school principal while I was bunking the class.My question is from Direction of Induced EMF topic in section Electromagnetism of Basic Electrical Engineering

Answer»

The CORRECT choice is (b) Fleming’s right hand rule

To explain: Fleming’s LEFT hand rule stated that if the INDEX finger points toward magnetic flux, the thumb TOWARDS the motion of the conductor, then the middle finger points towards the INDUCED emf.
Discussion
55.

The total number of magnetic field lines passing through an area is termed as?(a) Voltage(b) EMF(c) Magnetic flux(d) Magnetic flux densityThis question was posed to me in an international level competition.My question is based upon Electromagnetic Induction topic in chapter Electromagnetism of Basic Electrical Engineering

Answer»

Right answer is (c) MAGNETIC flux

Best EXPLANATION: Number of magnetic FIELD lines PASSING through an area is magnetic flux.
Discussion
56.

What does emf stand for?(a) Electronic magnetic force(b) Electromotive force(c) Electromagnetic force(d) Electromated forceI have been asked this question in semester exam.This intriguing question comes from Electromagnetic Induction topic in portion Electromagnetism of Basic Electrical Engineering

Answer»

The correct choice is (b) ELECTROMOTIVE FORCE

Easy explanation: Emf STANDS for electromotive force. It is the voltage developed by any source of electrical energy.
Discussion
57.

If the intensity of the magnetic field perpendicular to current carrying conductor is 100T, the length of the conductor is 3m and the current in the conductor is 10A, calculate the magnitude of force perpendicular to the electric field.(a) 300N(b) 30N(c) 30kN(d) 3kNThe question was asked in an interview.This intriguing question comes from Force Determination in portion Electromagnetism of Basic Electrical Engineering

Answer»

The correct OPTION is (d) 3kN

The BEST explanation: The formula for calculating the value of the force which is PERPENDICULAR to the magnetic field is:

F=Bil

Substituting the values from the question, we GET F=3kN.
Discussion
58.

The magnetic field of the solenoid is 18.84mT, the number of turns per unit length is 500 turns per metre. Calculate the current if the core is air.(a) 300A(b) 30A(c) 3A(d) 300mAI have been asked this question in an international level competition.I'm obligated to ask this question of Magnetic Field of a Solenoid topic in chapter Electromagnetism of Basic Electrical Engineering

Answer»

The correct answer is (b) 30A

Explanation: The MAGNETIC FIELD in a solenoid is given by:

B=μnI

Substituting the VALUES in the given values in the equation, I=30A.
Discussion
59.

When the distance of operation between the two conductors increases, what happens to the force between the two conductors?(a) Increases(b) Decreases(c) Remains the same(d) Becomes zeroThis question was addressed to me during an online interview.My question is taken from Magnetic Field Due to an Electric Current topic in chapter Electromagnetism of Basic Electrical Engineering

Answer»

The correct option is (b) Decreases

To explain: When the distance of separation increases, the FORCE between the TWO CONDUCTORS DECREASE because the force between two conductors is INVERSELY proportional to the distance of separation between them.
Discussion
60.

Weakest force in nature is?(a) Electric force(b) Gravitational force(c) Weak force(d) Magnetic forceI had been asked this question in a national level competition.My doubt stems from Magnetic Field in chapter Electromagnetism of Basic Electrical Engineering

Answer»

Right choice is (b) Gravitational force

The BEST I can explain: Gravitational force is the weakest force in nature as it does not bind ANYTHING strongly with its HELP.
Discussion
61.

According to Faraday’s laws of electromagnetic induction, an emf is induced in a conductor whenever?(a) The conductor is perpendicular to the magnetic field(b) Lies in the magnetic field(c) Cuts magnetic lines of flux(d) Moves parallel to the magnetic fieldThe question was asked in my homework.I'm obligated to ask this question of Direction of Induced EMF topic in chapter Electromagnetism of Basic Electrical Engineering

Answer»

Right CHOICE is (c) Cuts magnetic lines of FLUX

Easiest EXPLANATION: An emf is induced, according to Faraday’s LAWS of ELECTROMAGNETIC induction, whenever the conductor in a magnetic field cuts the magnetic lines of flux.
Discussion
62.

When the current in the current carrying conductor increases, what happens to the force in the conductor which is at right angles to the magnetic field?(a) Increases(b) Decreases(c) Remains the same(d) Becomes zeroI got this question by my school teacher while I was bunking the class.My question is taken from Force Determination in portion Electromagnetism of Basic Electrical Engineering

Answer»

Correct OPTION is (a) Increases

To ELABORATE: The FORCE at right ANGLES to the magnetic field of a current CARRYING conductor increases when the current increases because it is directly proportional to the force.
Discussion
63.

What is the formula for the magnetic field due to a solenoid?(a) μnI(b) μn^2(c) μNI(d) μN^2I^2This question was addressed to me in unit test.I'm obligated to ask this question of Magnetic Field of a Solenoid topic in section Electromagnetism of Basic Electrical Engineering

Answer»

Correct answer is (a) μnI

The best I can explain: The MAGNETIC FIELD due to a solenoid is:

B= μnI, where μ is the permeability, n is the NUMBER of turns per unit LENGTH and I is the CURRENT in the solenoid.
Discussion
64.

If current of conductor increases, what is the effect on the force?(a) increases(b) decreases(c) remain same(d) become zeroThe question was posed to me in an online quiz.Question is taken from Magnetic Field Due to an Electric Current in portion Electromagnetism of Basic Electrical Engineering

Answer»

Right CHOICE is (a) increases

The explanation is: Force of infinite conductor is given by BIL if B, i, l are mutually perpendicular

F/l = BI = µ0i1i2/2πd if d is separation of two infinite parallel conductors. So, as CURRENT increases force increases.
Discussion
65.

The force per unit length existing between two infinite parallel conductors is given by ___________(a) µ0i1i2/2πd(b) µ0i1i2/2d(c) µ0i1/2πdi2(d) µ0i1i2/dThis question was posed to me during an online exam.This is a very interesting question from Magnetic Field Due to an Electric Current topic in portion Electromagnetism of Basic Electrical Engineering

Answer»

The correct answer is (a) µ0i1i2/2πd

For EXPLANATION I would say: Force of INFINITE conductor is given by Bil if B, i, l are MUTUALLY perpendicular

F/l = BI = µ0i1i2/2πd if d is SEPARATION of two infinite parallel conductors.
Discussion
66.

An E.M.F. can be induced by _________(a) Change in the magnetic field only(b) Change in the area of cross section only(c) Change in angle between magnetic field and area only(d) Change in the magnetic field, area or angle between themI had been asked this question in semester exam.This intriguing question comes from Electromagnetic Induction in section Electromagnetism of Basic Electrical Engineering

Answer»

The correct option is (d) CHANGE in the magnetic field, area or ANGLE between them

Explanation: emf=-dϕ/dt. We know ϕ FLUX is the dot PRODUCT of magnetic field vector and area vector.

ϕ=BAcos(θ), hence if either of the three, that is, magnetic field, area or angle changes, the emf will change, flux changes due to which emf can be induced.
Discussion
67.

Which, among the following, is the formula for induced emf?(a) e=dϕ /dt(b) e=dt/dϕ(c) e=t*ϕ(d) e=t^2ϕThis question was addressed to me in final exam.The doubt is from Magnitude of the Generated or Induced EMF in division Electromagnetism of Basic Electrical Engineering

Answer»

Right ANSWER is (a) E=dϕ /dt

The explanation is: The formula for INDUCED emf is e = dϕ /dt because the induced emf is the flux LINKAGE per unit time.
Discussion
68.

The magnetic field strength of a solenoid can be increased by inserting which of the following materials as the core?(a) Copper(b) Silver(c) Iron(d) AluminiumI had been asked this question by my school principal while I was bunking the class.I want to ask this question from Magnetic Field of a Solenoid topic in portion Electromagnetism of Basic Electrical Engineering

Answer» RIGHT choice is (c) Iron

Easy EXPLANATION: The Magnetic field of a solenoid increases when we insert an iron core because iron is a ferromagnetic MATERIAL and ferromagnetic materials help in INCREASING the magnetic property.
Discussion
69.

Inside the magnet, field lines travel from?(a) North to south(b) South to north(c) West to east(d) East to westI got this question during an online interview.My question is from Characteristics of Lines of Magnetic Flux topic in section Electromagnetism of Basic Electrical Engineering

Answer»

The correct answer is (b) South to north

Explanation: MAGNETIC field LINES ORIGINATE at the north pole and terminate at the south pole of the magnet and magnetic field lines FORM closed loop so INSIDE the magnet, they move from south to north.
Discussion
70.

According to Fleming’s right hand rule, the middle finger points towards?(a) Current(b) E.M.F.(c) Motion of the conductor(d) Magnetic fluxThis question was posed to me in examination.I need to ask this question from Direction of Induced EMF in chapter Electromagnetism of Basic Electrical Engineering

Answer»

The correct answer is (b) E.M.F.

For explanation I would say: Fleming’s left hand rule stated that if the index FINGER points towards magnetic flux, the THUMB towards the motion of the CONDUCTOR, then the MIDDLE finger points towards the induced emf.
Discussion
71.

According to Flemming’s left hand rule, the middle finger denotes?(a) Direction of magnetic field(b) Direction of current(c) Direction of force(d) Direction of force as well as currentThe question was posed to me in class test.My query is from Direction of Magnetic Field in chapter Electromagnetism of Basic Electrical Engineering

Answer»

Right ANSWER is (b) Direction of CURRENT

The best explanation: According to Flemming’s left hand rule, the INDEX finger denotes the direction of the magnetic field, the thumb denoted the direction of force and the MIDDLE finger denoted the direction of the current.
Discussion
72.

What is the magnetic field outside a solenoid?(a) Infinity(b) Half the value of the field inside(c) Double the value of the field inside(d) ZeroThe question was posed to me during an online exam.The above asked question is from Magnetic Field in section Electromagnetism of Basic Electrical Engineering

Answer» RIGHT option is (d) Zero

To explain I would say: There are no MAGNETIC LINES of FORCE outside a solenoid, hence the magnetic field outside a solenoid is zero.
Discussion
73.

What is emf?(a) Force(b) Voltage(c) Current(d) FluxThis question was posed to me during an interview.My enquiry is from Electromagnetic Induction in portion Electromagnetism of Basic Electrical Engineering

Answer» RIGHT answer is (b) Voltage

The best explanation: ELECTROMOTIVE force is not ACTUALLY a force. It is basically a voltage. It is the voltage DEVELOPED by any source of electrical energy.
Discussion
74.

Weakest force in nature is __________(a) Electric force(b) Gravitational force(c) Weak force(d) Magnetic forceI got this question during an interview for a job.Question is taken from Force on a Current Carrying Conductor topic in chapter Electromagnetism of Basic Electrical Engineering

Answer»

The correct ANSWER is (a) Electric FORCE

Explanation: Gravitational force is the weakest force in nature as it does not bind anything strongly with its help.
Discussion
75.

Force in a conductor is __________ to the square of the distance between the charges.(a) Directly proportional(b) Inversely proportional(c) Not related(d) Cannot be determinedI got this question during an online exam.The origin of the question is Force on a Current Carrying Conductor topic in section Electromagnetism of Basic Electrical Engineering

Answer» CORRECT option is (b) Inversely proportional

For explanation: The FORCE in a current carrying conductor is directly proportional to the PRODUCT of the two CHARGES and inversely proportional to the square of the DISTANCE between them.
Discussion
76.

If length of current carrying conductor increases, what is the effect on the force?(a) increases(b) decreases(c) remain same(d) become zeroI had been asked this question during an interview.My query is from Magnetic Field Due to an Electric Current topic in chapter Electromagnetism of Basic Electrical Engineering

Answer» RIGHT choice is (a) increases

The best I can EXPLAIN: Force of infinite conductor is given by Bil if B, i, l are mutually perpendicular

F/l = Bi = µ0i1i2/2πd if d is a SEPARATION of two infinite parallel conductors. So, as LENGTH of conductor increases force increases.
Discussion
77.

Magnetic Field lines move from _______(a) North to south(b) South to north(c) West to east(d) East to westI have been asked this question during an internship interview.This is a very interesting question from Magnetic Field topic in section Electromagnetism of Basic Electrical Engineering

Answer»

The correct CHOICE is (a) North to south

For EXPLANATION: MAGNETIC field lines originate at the north POLE and terminate at the south pole of the MAGNET.
Discussion
78.

The ratio of magnetic force to electric force on a charged particle getting undeflected in a field is?(a) 1(b) 0(c) 2(d) 4I have been asked this question in an interview for job.Asked question is from Magnetic Field topic in chapter Electromagnetism of Basic Electrical Engineering

Answer» CORRECT answer is (a) 1

Easiest explanation: When a charged PARTICLE is undeflected in a FIELD, the magnitude of the magnetic FORCE and electric force acting on the particle is the same, hence the ratio is 1.
Discussion
79.

If the flow of electric current is parallel to the magnetic field, the force will be ______(a) Zero(b) Infinity(c) Maximum(d) Half the original valueI have been asked this question in homework.This interesting question is from Magnetic Field in section Electromagnetism of Basic Electrical Engineering

Answer» CORRECT choice is (a) ZERO

The explanation is: FORCE is a cross product. A cross product involves the sine of the angle between them. If two quantities are parallel to each other, the angle between them is zero. Sin(0) is zero, HENCE force is zero.
Discussion
80.

When a charged particle moves at right angles to the magnetic field, the variable quantity is?(a) Momentum(b) Speed(c) Energy(d) Moment of inertiaThe question was posed to me during an interview for a job.This is a very interesting question from Magnetic Field in chapter Electromagnetism of Basic Electrical Engineering

Answer»

Correct OPTION is (a) MOMENTUM

The EXPLANATION is: When a charged particle moves perpendicular to the field, its speed remains the same whereas its velocity keeps on changing. Momentum is the PRODUCT of the mass of the particle and the velocity if the particle, hence since velocity VARIES, momentum also varies.
Discussion
81.

When the length of the conductor in the current carrying conductor increases, what happens to the force in the conductor which is at right angles to the magnetic field?(a) Increases(b) Decreases(c) Remains the same(d) Becomes zeroI got this question in a job interview.My question is from Force Determination topic in division Electromagnetism of Basic Electrical Engineering

Answer»

Correct OPTION is (a) INCREASES

The best I can explain: The FORCE at right angles to the magnetic field of a current carrying conductor increases when the length of the conductor increases because it is DIRECTLY proportional to the force.
Discussion
82.

Voltage induced in secondary coil of transformer is given by__________________(a) NP*VP/NS(b) NS*VP/NP(c) (NP/VP)*NS(d) NP/(VP*NS)I had been asked this question in quiz.The question is from Magnitude of the Generated or Induced EMF topic in section Electromagnetism of Basic Electrical Engineering

Answer» RIGHT ANSWER is (b) NS*VP/NP

The explanation is: In TRANSFORMER, VP/VS = NP/NS

So, VS = NS*VP/NP.
Discussion
83.

Do magnetic flux lines intersect?(a) Yes(b) No(c) Depends on the situation(d) Cannot be determinedThe question was posed to me in an interview.This is a very interesting question from Characteristics of Lines of Magnetic Flux in section Electromagnetism of Basic Electrical Engineering

Answer»

The correct answer is (b) No

The best explanation: MAGNETIC field lines do not cross each other because if they cross each other it MEANS that there are TWO different directions of a magnetic field in that REGION and that is not possible.
Discussion
84.

According to ____________________ induced emf oppose the cause due to which they are produced.(a) Newton’s law(b) Lenz law(c) Faraday’s law(d) Coulomb’s lawI have been asked this question in class test.I need to ask this question from Magnitude of the Generated or Induced EMF topic in section Electromagnetism of Basic Electrical Engineering

Answer» RIGHT OPTION is (b) Lenz law

The EXPLANATION: According to Lenz law, emf is induced in such a way that it opposes the CAUSE due to which it is produced.
Discussion
85.

If the flow of electric current is parallel to the magnetic field, the force will be?(a) Zero(b) Infinity(c) Maximum(d) Half the original valueI had been asked this question by my school principal while I was bunking the class.Asked question is from Force on a Current Carrying Conductor topic in section Electromagnetism of Basic Electrical Engineering

Answer» RIGHT answer is (a) Zero

To elaborate: Force is a cross product. A cross product involves the SINE of the angle between them. If TWO quantities are parallel to each other, the angle between them is zero. Sin(0) is zero, HENCE force is zero.
Discussion
86.

If the radius of the current carrying conductor increases, what is the effect on the force?(a) increases(b) decreases(c) remain same(d) become zeroI had been asked this question by my college professor while I was bunking the class.I'm obligated to ask this question of Magnetic Field Due to an Electric Current topic in division Electromagnetism of Basic Electrical Engineering

Answer»

The CORRECT choice is (c) remain same

For EXPLANATION I WOULD say: Force of the INFINITE conductor is given by Bil if B, i, l are mutually perpendicular

F/l = Bi = µ0i1i2/2πd if d is separation of TWO infinite parallel conductors. It doesn’t depend on the radius of conductor so force remains the same.
Discussion
87.

The relation between the direction of current and the direction of the force is _________(a) Same direction(b) Opposite direction(c) Perpendicular(d) UnrelatedThe question was posed to me in semester exam.The doubt is from Direction of Magnetic Field topic in chapter Electromagnetism of Basic Electrical Engineering

Answer»

Right ANSWER is (c) Perpendicular

To explain I would SAY: When a conductor carries a certain VALUE of CURRENT, the force developed in the conductor, the current in the conductor and the magnetic FIELD in the conductor are mutually perpendicular to each other.
Discussion