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# Multiple choice question for engineering

## Set 1

1. Field lines move from __________
a) North to south
b) South to north
c) West to east
d) East to west

Answer: a [Reason:] Magnetic field lines originate at the north pole and terminate at the south pole of the magnet.

2. Magnetic field lines ___________ at the north pole.
a) Emerge
b) Converge
c) Neither emerge nor converge
d) Either emerge or converge

Answer: a [Reason:] Magnetic field lines emerge at the north pole. Field lines seem to emerge at the north pole because they originate at the north pole.

3. Magnetic field lines ___________ at the south pole.
a) Emerge
b) Converge
c) Neither emerge nor converge
d) Either emerge or converge

Answer: b [Reason:] Magnetic field lines converge at the south pole. Field lines seem to converge at the south pole because they end at the south pole.

4. Which of the following is used to determine the direction of magnetic field in a current carrying conductor?
a) Left hand thumb rule
b) Right hand thumb rule
c) Right hand palm rule
d) Left hand palm rule

Answer: b [Reason:] The right hand thumb rule determines the direction of magnetic field in a current carrying conductor. The rule states that when we align our right thumb in the direction of the current and curl our fingers around it, the direction of our fingers is the direction of the magnetic field.

5. According to Flemming’s left hand rule, the index finger denotes?
a) Direction of magnetic field
b) Direction of current
c) Direction of force
d) Direction of force as well as current

Answer: a [Reason:] According to Flemming’s left hand rule, the index finger denotes the direction of magnetic field, the thumb denoted the direction of force and the middle finger denoted the direction of current.

6. 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 current

Answer: b [Reason:] According to Flemming’s left hand rule, the index finger denotes the direction of magnetic field, the thumb denoted the direction of force and the middle finger denoted the direction of current.

7. According to Flemming’s left hand rule, the thumb denotes?
a) Direction of magnetic field
b) Direction of current
c) Direction of force
d) Direction of force as well as current

Answer: c [Reason:] According to Flemming’s left hand rule, the index finger denotes the direction of magnetic field, the thumb denoted the direction of force and the middle finger denoted the direction of current.

8. The relation between the direction of force and the direction of magnetic field is _________
a) Same direction
b) Opposite direction
c) Perpendicular
d) Unrelated

Answer: c [Reason:] 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.

9. The relation between the direction of current and the direction of magnetic field is ________
a) Same direction
b) Opposite direction
c) Perpendicular
d) Unrelated

Answer: c [Reason:] 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.

10. The relation between the direction of current and the direction of force is _________
a) Same direction
b) Opposite direction
c) Perpendicular
d) Unrelated

Answer: c [Reason:] 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.

## Set 2

1. The current in conductors connecting the voltage source to the plates of a capacitor is _______
a) Conduction current
b) Leakage current
c) Charging current
d) Displacement current

Answer: c [Reason:] The current in conductors connecting the voltage source to the plates of a capacitor is the charging current and not the conduction or leakage current.

2. What is the type of current where the electrons actually move?
a) Displacement current
b) Conduction current
c) Both conduction and displacement current
d) Neither conduction nor displacement current

Answer: b [Reason:] Conduction current is the current caused by the actual flow of electrons and displacement current is the current where no charge carriers are involved.

3. What is the type of current caused due to variations in the field?
a) Displacement current
b) Conduction current
c) Both conduction and displacement current
d) Neither conduction nor displacement current

Answer: a [Reason:] Displacement current is the current where no charge carriers are involved. It is caused due to variations in the electric field.

4. Under normal conditions capacitors have _______
a) Displacement current
b) Conduction current
c) Both conduction and displacement current
d) Neither conduction nor displacement current

Answer: a [Reason:] Under normal conditions capacitors contain an insulating material called dielectric sandwiched between the plates of the capacitor. Since insulators can carry only an electric field but not moving carriers, therefore normally a capacitor has displacement current and not conduction current.

5. If a large amount of voltage is applied to a capacitor, what is the current that flows through it?
a) Displacement current
b) Conduction current
c) Both conduction and displacement current
d) Neither conduction nor displacement current

Answer: b [Reason:] When a large amount of voltage is applied between the plates of a capacitor, the dielectric between the plates does not behave as an insulator anymore and starts conducting and conduction currents flow through it and not displacement current.

6. What is the unit for displacement current?
a) No unit
b) Ampere
c) Coulomb
d) Ampere/coulomb

Answer: b [Reason:] Displacement current is a type of current and hence it has the same unit as that of current that is ampere.

7. Displacement current depends on ___________
a) Moving charges
b) Change in time
c) Both moving charges and change in time
d) Neither moving charges nor change in time

Answer: b [Reason:] Displacement current is the current which arises due to variations in the field. Hence, it does not depend on the moving charges but due to change in time which causes variation in the field.

8. Magnetic fields between the parallel plates of a capacitor is due to?
a) Displacement current
b) Conduction current
c) Both conduction and displacement current
d) Neither conduction nor displacement current

Answer: a [Reason:] Displacement current is the current which arises due to variations in the field. Change in the field results in the formation of magnetic fields. Hence displacement currents lead to magnetic field between the plates of a capacitor.

9. The free electrons in practical dielectrics are due to ________
a) There are no free electrons
b) Conductors
c) Impurities
d) Displacement currents

Answer: c [Reason:] Ideally, dielectrics are insulators and do not contain any free electrons. But no dielectric is a perfect dielectric, hence the free electrons are due to impurities present in each dielectric.

10. The flow of electrons which does not pass through the battery is known as ____________
a) Conduction current
b) Leakage current
c) Charging current
d) Displacement current

Answer: a [Reason:] Conduction current is the flow of electrons from the positive plate of the capacitor to the negative plate of the capacitor, not through the battery. Hence the type of current which flows without passing through the battery is conduction current.

## Set 3

1. Gauss law is applicable for_________
a) Point charge
b) Sheet charge
c) Line charge
d) Point, sheet and line charge

Answer: d [Reason:] Gauss law states that the total electric flux through any closed surface is equal to the charge enclosed by that surface.Hence it is applicable for all point, surface and volume.

2. “Total electric flux through any closed surface is equal to the charge enclosed by that surface”. This is the statement for?
a) Gauss law
b) Lenz law
c) Coloumb’s law

Answer: a [Reason:] Total electric flux through any closed surface is equal to the charge enclosed by that surface is the statement for Gauss law because among the four laws, Gauss law deals with electric flux.

3. Electric flux density is a function of_______
a) Volume
b) Charge
c) Current
d) Voltage

Answer: b [Reason:] Electric flux density is the charge per unit area. Hence it is a function of charge and not any of the other values.

4. As charge increases, what happens to flux density?
a) Increases
b) Decreases
c) Remains constant
d) Becomes zero

Answer: a [Reason:] Electric flux density is the charge per unit area. The expression for flux density is: D=Q/A. Electric flux is directly proportional to charge, hence as charge increases, electric flux also increases.

5. As area increases, what happens to electric flux density?
a) Increases
b) Decreases
c) Remains constant
d) Becomes zero

Answer: b [Reason:] Electric flux density is the charge per unit area. The expression for flux density is: D=Q/A. Electric flux is inversely proportional to area, hence as area increases, electric flux decreases.

6. Which, among the following, is the correct expression for electric flux density?
a) D=epsilon*E
b) D=epsilon/E
c) D2=epsilon*E
d) D=epsilon*E2

Answer: a [Reason:] Electric flux density is directly proportional to the electric field, epsilon(permittivity of free space) being the constant of proportionality. Hence D=epsilon*E.

7. Strength of the electric field is ___________
a) Directly proportional to the force applied
b) Inversely proportional to the force applied
c) Directly proportional to the square of the force applied
d) Inversely proportional to the square of the force applied

Answer: a [Reason:] Electric field intensity is the force per unit charge, hence it id directly proportional to the force applied.

8. The force applied to a conductor is 10N, if the charge in the conductor is 5C, what is the electric field intensity?
a) 10V/m
b) 2V/m
c) 3V/m
d) 15V/m

Answer: b [Reason:] Electric field intensity is the force per unit charge. The formula is: E=F/Q= 10/5= 2V/m.

9. What is the electric flux density in free space if the electric field intensity is 1V/m?
a) 7.76*10-12C/m2
b) 8.85*10-12C /m2
c) 1.23*10-12C /m2
d) 3.43*10-12C /m2

Answer: b [Reason:] The formula for electric filed density is: D=epsilon*E= 1*8.85*110-12= 8.85*10-12C /m2.

10. If the charge in a conductor is 16C and the area of cross section is 4m2. Calculate the electric flux density.
a) 64C/m2
b) 16C/m2
c) 4C/m2
d) 2C/m2

Answer: c [Reason:] Flux density is the charge per unit area. The formula is: D=Q/A= 16/4= 4C/m2.

## Set 4

1. The conventional direction of electric field is ________
a) Positive to negative
b) Negative to positive
c) No specific direction
d) Direction cannot be determined

Answer: a [Reason:] The conventional direction of field lines is from positive to negative. The field lines originate at the positive charge and terminate at the negative charge.

2. Electric field originates at __________
a) Positive charge
b) Negative charge
c) Neither positive nor negative
d) Both positive and negative

Answer: a [Reason:] Electric field originates at the positive charge and terminates at the negative charge. The conventional direction of field is from positive to negative.

3. Electric field terminates at ________
a) Positive charge
b) Negative charge
c) Neither positive nor negative
d) Both positive and negative

Answer: b [Reason:] Electric field originates at the positive charge and terminates at the negative charge. The conventional direction of field is from positive to negative.

4. Which among the following statements is true with regard to electric field lines?
a) Electric field lines always intersect
b) Electric field lines may or may not intersect
c) Electric field lines can be seen
d) Electric field lines never intersect

Answer: d [Reason:] Electric field lines can never intersect because the field lines represent the field strength. If the lines intersect it means that at that point there are two different values for electric field which is not possible.

5. Which, among the following, is the field where electric charge experiences a force?
a) Electric field
b) Magnetic field
c) Gravitational field
d) Electric, magnetic or gravitational field

Answer: a [Reason:] Charges experience a force in an electric field because charges come under the influence of a field which already has charges- electric field.

6. A field that spreads outwards in all directions is __________
a) Linear
c) Weak
d) Strong

Answer: b [Reason:] A radial field is one which spreads in all directions. This field is known as the radial field because it spreads out radially from a source.

7. In uniform fields, all points have ________ field strength.
a) Zero
b) Same
c) Infinity
d) Different

Answer: b [Reason:] A uniform field is one-as the word suggests-in which the field is spread over an area and at every point in the field the, strength of the field is the same.

8. Which, among the following is the correct expression for electric field?
a) E=F/C
b) E=F*C
c) E=F/Q
d) E=F*Q

Answer: c [Reason:] Electric field is the force per unit charge hence, the correct expression among the following is: E=F/Q.

9. What happens when one material is rubbed against another?
a) The material becomes electrically neutral
b) The material becomes electrically charged
c) The material becomes negatively charged
d) The material becomes positively charged

Answer: b [Reason:] When one material is rubbed against another, there is transfer of charges from one material to another hence the material becomes electrically charged.

10. The insulant between the two plates of a capacitor is called _______
a) Conductor
b) Semi-conductor
c) Dielectric
d) Superconductor

Answer: c [Reason:] The material between the two plates of a capacitor is an insulator, more specifically known as a dielectric.

## Set 5

1. An E.M.F. can be induced by _________
a) Change in magnetic field
b) Change in the area of cross section
c) Change in angle between magnetic field and area
d) Change in magnetic field, area and angle

Answer: d [Reason:] It is the dot product of magnetic field vector and area vector. emf=BAcos(theta), hence if either of the three, that is, magnetic field, area or angle changes, thee emf will change.

2. What happens to the current in a coil while accelerating a magnet inside it?
a) Increases
b) Decreases
c) Remains constant
d) Reverses

Answer: a [Reason:] A chance in magnetic field induces an emf. When there is an emf, there has to be a current. Hence, when the magnet is moved inside a coil, the current in it increases.

3. What is the consequence of motor effect?
a) Current
b) Voltage
c) Electromagnetic induction
d) EMF

Answer: c [Reason:] Motor effect is when a current carrying conductor in a magnetic field experiences a force, hence its consequence is electromagnetic induction.

4. The total number of magnetic field lines passing through an area is termed as?
a) Voltage
b) EMF
c) Magnetic flux
d) Magnetic flux density

Answer: b [Reason:] The number of magnetic flux lines per unit area is the magnetic flux, because flux is the number of field lines per unit area.

5. The formula for induced emf is __________
a) emf=B2l
b) emf=Bil
c) emf=Blv
d) emf=B2v

Answer: c [Reason:] The formula for induced emf is: emf=Blv, where B is the magnetic field, l is the length of the conductor and v is the velocity with which it is moving in the magnetic field.

6. If a conductor 0.2m long moves with a velocity of 0.3m/s in a magnetic field of 5T, calculate the emf induced.
a) 0.3V
b) 0.03V
c) 30V
d) 3V

Answer: a [Reason:] The formula for induced emf is: emf=Blv. Substituting the values of B, l and v from the question, we get emf=0.3V.

7. Find the length of a conductor which is moving with a velocity 0.4m/s in a magnetic field of 8T, inducing an emf of 20V.
a) 50m
b) 5m
c) 6.25m
d) 0.5m

Answer: c [Reason:] The formula for induced emf is: emf=Blv. Substituting the values of B, emf and v from the question, we get l=6.25m.

8. Find the strength of magnetic field in a conductor 0.5m long moving with a velocity of 10m/s, inducing an emf of 20V.
a) 1T
b) 2T
c) 3T
d) 4T

Answer: d [Reason:] The formula for induced emf is: emf=Blv. Substituting the values of l, emf and v from the question, we get B=4T.

9. What does emf stand for?
a) Electronic magnetic force
b) Electromotive force
c) Electromagnetic force
d) Electromated force