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Previous year question Of Magnetic Effects of Electric Current and Magnetism For NDA

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Previous year question Of Magnetic Effects of Electric Current and Magnetism

Previous year question
Q 2763091845

Which one of the following devices changes low voltage alternating current to high voltage alternating current and vice versa?
NDA Paper 2 2017
(A)

Generator

(B)

Motor

(C)

Transforrner

(D)

Vibrator

Solution:

A transformer is an electrical device that works on principal of mutual induction to convert a given AC voltage into a larger voltage (step-up transformer) or a lower voltage (step-down transformer).
Correct Answer is `=>` (C) Transforrner
Q 2783191947

At which place Earth magnetic field becomes horizontal.?
NDA Paper 2 2017
(A)

Magnetic meridian

(B)

Magnetic equator

(C)

Geographical pole

(D)

Tropic of Cancer

Solution:

A transformer is an electrical device that works on principal of mutual induction to convert a given AC voltage into a larger voltage (step-up transformer) or a lower voltage (step-down transformer).
Correct Answer is `=>` (B) Magnetic equator
Q 2784212157

In a solenoid, the current flowing through the wire, is `I` and number of tums per unit length is n. This gives a magnetic field B inside the solenoid. If number of tum per unit lengthwise increased to 2n, what will be the value of magnetic field in.the solenoid ?
NDA Paper 2 2017
(A)

B

(B)

2B

(C)

B/2

(D)

B/4

Solution:

A transformer is an electrical device that works on principal of mutual induction to convert a given AC voltage into a larger voltage (step-up transformer) or a lower voltage (step-down transformer).
Correct Answer is `=>` (B) 2B
Q 2343178043

Which one among the following properties of a proton may change, while it moves freely in a magnetic field?
NDA Paper 2 2013
(A)

Speed

(B)

Charge

(C)

Mass

(D)

Velocity

Solution:

Proton move is circle and velocity change as its direction change.
Correct Answer is `=>` (D) Velocity
Q 2314412359

The motion of an electron in presence of a magnetic field is depicted in the figure given above. The force acting on the electron will be directed.
NDA Paper 2 2013
(A)

into the page

(B)

out of the page

(C)

opposite to the motion of the electron

(D)

along the motion of the electron

Solution:

According fo Fleming left hand rule, when the current flows in a wire and an external magnetic field is applied across that flow, the wire experience a force perpendicular both to that fielcl and to the direction of the current flow. So, the force acting on the electron will be directed out of the page
Correct Answer is `=>` (B) out of the page
Q 2304012858

Imagine a current carrying wire with the direction of current downward or into the page. The direction of magnetic field lines is.
NDA Paper 2 2013
(A)

clockwise

(B)

anti-clockwise

(C)

into the page

(D)

out of the page

Solution:

According to the right hand thumb rule, the direction of magnetic field lines is in clockwise direction.
Correct Answer is `=>` (A) clockwise
Q 2384323257

A current carrying wire is known to produce magnetic lines of force around the conducting straight wire. The direction of the lines of force may be described by.
NDA Paper 2 2013
(A)

left hand thumb rule for up current and right hand thumb rule for down current

(B)

right hand thumb rule for up current and left hand thumb rule for down current

(C)

right hand thumb rule for both up and down currents

(D)

left hand thumb rule for both up and down currents

Solution:

The direction of the lines of force may be described by right-hand thumb rule for both up and down currents.
Correct Answer is `=>` (C) right hand thumb rule for both up and down currents
Q 2374723656

A positively charged particle projected towards West is deflected towards North by a magnetic field. The direction of the magnetic field is.
NDA Paper 2 2013
(A)

towards South

(B)

towards East

(C)

in downward direction

(D)

in upward direction

Solution:

The direction of the lines of force may be described by right-hand thumb rule for both up and down currents.
Correct Answer is `=>` (D) in upward direction
Q 2364045855

The earth's magnetic field is approximately
NDA Paper 2 2012
(A)

1 Tesla

(B)

2 Gauss

(C)

`10^4` Tesla

(D)

1 Gauss

Solution:

Earth's magnetic field (also known as the geomagnetic field) is the magnetic field that extends from the Earth's inner core to where it meets the solar wind, a stream of energetic particles emanating from the Sun. Its magnitude at the Earth's surface ranges from `0.25` to `0.65` Gauss.
Correct Answer is `=>` (D) 1 Gauss
Q 2324656551

The polarity of an unmarked horse shoe magnet can be determined by using
NDA Paper 2 2012
(A)

a charoed olass rod

(B)

a magnetic compass

(C)

an electroscope

(D)

another unmarked bar magnet

Solution:

The polarity of an unmarked horse shoe magnet can be determined by using a magnetic compass.
Correct Answer is `=>` (B) a magnetic compass
Q 2334756652

Consider. the following statements
1 . If a piece of bar magnet is broken into two equally long pieces, the pieces will not lose the magnetic properties.
2. Magnetic properties of a substance lie in the atomic level.
Which of the statement(s) given alone is/are correct?
NDA Paper 2 2012
(A)

Only 1

(B)

Only 2

(C)

Both 1 and 2

(D)

Neither 1 nor 2

Solution:

Both the given option is correct. If a pieces of bar magnet is broken into two equally long pieces, the pieces will not lose the magnetic properties. Magnetic properties of a substance lie in the atomic level.
Correct Answer is `=>` (C) Both 1 and 2
Q 2374480356

For which among the following house appliances, magnet is an essential part?
NDA Paper 2 2012
(A)

Calling bell

(B)

Fan

(C)

Washing machine

(D)

All of these

Solution:

All the given things have magnet as an essential part.
Correct Answer is `=>` (D) All of these
Q 2334780652

The torque on a rectangular coil placed in a uniform magnetic field is large when the
NDA Paper 2 2012
(A)

number of turns is large

(B)

number of turns is less

(C)

plane of the coil is perpendicular to the magnetic field

(D)

area of the coil is small

Solution:

When the number of turns is large.
Correct Answer is `=>` (A) number of turns is large
Q 2364080855

A neutral (uncharged) metal ball is suspended using a non-magnetic string. A positively charged insulating rod is placed near the ball which is observed to be attracted to the rod. This is because
NDA Paper 2 2011
(A)

the ball becomes positively charged by induction

(B)

the ball becomes negatively charged by induction

(C)

there is a rearrangement of the electrons in the ball

(D)

the number of electrons in the ball is more than the number of electrons on the rod

Solution:

According to the induction principle, when we placed a positively charged rod near the ball, then the negative charge will increase in the ball to the front of the rod and the positive charge will increase in the back of the ball (far from the rod). By this, rearrangement of electrons takes place.
Correct Answer is `=>` (C) there is a rearrangement of the electrons in the ball
Q 2315723660

The lines of force of uniform magnetic field
NDA Paper 2 2011
(A)

must be convergent

(B)

must be divergent

(C)

must be parallel to each other

(D)

intersect

Solution:

Magnetic field can be represented with the help of a set
of lines or curves called magnetic field lines. These lines are not
real but are drawn to visualise the magnetic field. In a uniform
magnetic field, the magnitude as well as direction of the strength
of magnetic field remains the same throughout the region.
Uniform rnagnetic field is represented by an equidistant set of
parallel lines.
Correct Answer is `=>` (C) must be parallel to each other
Q 2315034869

Magnets attract magnetic: substances as iron, nickel, cobalt, etc. They can also repel
NDA Paper 2 2011
(A)

paramagnetic substances

(B)

ferromagnetic substances

(C)

diamagnetic substances

(D)

non-magnetic substances

Solution:

The materials which are weakly magnetised in a direction opposite to the direction of applied magnetic field are known as diamagnetic materials. So, diamagnetic substances are repelled by magnet.
Correct Answer is `=>` (C) diamagnetic substances
Q 2385445367

Magnetism of a bar magnet can be destroyed if it is
(1) kept in the magnetic meridian
(2) placed in a direction opposite to that of the Earth's horizontal intensity.
(3) heated to a temperature known as Curie temperature.
NDA Paper 2 2010
(A)

1 and 3

(B)

Only 2

(C)

2 and 3

(D)

All of the above

Solution:

The magnetism of a bar magnet can be destroyed.
(i) By placing the magnet in a direction opposite to that of the Earth's horizontal intensity.
(ii) Curie temperature of iron is about `770^o C`. When a magnet is heated above Curie temperature its magnetism is lost and can not be retained.
Correct Answer is `=>` (C) 2 and 3
Q 2335045862

The direction of magnetic field at a point due to an infinitely long wire carrying current is
NDA Paper 2 2010
(A)

parallel to the current

(B)

antiparallel to the current

(C)

along the perpendicular drawn from a point on the wire

(D)

perpendicular to the plane containing the conductor and the point

Solution:

The direction of magnetic field at a point due to an infinitely long wire carrying current is perpendicular to the plane containing the conductor and the point.
Correct Answer is `=>` (D) perpendicular to the plane containing the conductor and the point
Q 2355678564

The magnetic lines of force due to the bar
magnet
NDA Paper 2 2010
(A)

intersect inside the body of the magnet

(B)

intersect at neutral points only

(C)

intersect only at north and south poles

(D)

cannot intersect at all

Solution:

The two magnetic lines of force due to a bar magnet do
not intersect or cross each other because if they cross each
other, then at the point of intersection these will be two directions
of the magnetic field which is not possible.

Hence, option (4) is the right answer.
Correct Answer is `=>` (D) cannot intersect at all
Q 2345778663

Which one of the statements given below is not correct'?
NDA Paper 2 2010
(A)

A vertical plane passing through the axis of a freely suspended magnet is called the magnetic meridian

(B)

A vertical plane passing through the axis of rotation of the Earth is called the geographical meridian

(C)

The degree to whici1 the maonetic field can penetrate a medium is known as the relative permeability of the medium

(D)

The relative permeability is not a dimensionless quantity

Solution:

Magnetic meridian A vertical plane passing through the magnetic axis of freely suspended magnet. Geographical meridian A vertical plane passing through the geographical axis (axis of rotation of Earth). Relative permeability The degree to which the magnetic field can penetrate a medium. It is given as `mu_r= mu/(mu_0)` It is unitless and hence, no dimensions.
Correct Answer is `=>` (D) The relative permeability is not a dimensionless quantity
Q 2376634576

If an `alpha`-particle is projected normally through a uniform magnetic field, then the path of the `alpha`-particle inside the field will be
NDA Paper 2 2009
(A)

circular

(B)

parabolic

(C)

elliptic

(D)

a straight line

Solution:

If an `alpha`-particle is projected normally through a uniform magnetic field, then a magnetic force acts on it which is perpendicular to its velocity so that the path of the `alpha`-particle inside the field will be circular.
Correct Answer is `=>` (A) circular
Q 2316856770

A proton and an electron having equal velocity are allowed to pass through a uniform magnetic field. Which one of the following statements is correct in this connection?
NDA Paper 2 2008
(A)

The proton and the electron experience equal and opposite force

(B)

The proton experiences greater force than does the electron

(C)

The electron experiences more force than does the proton

(D)

No moving charged particle experiences a force in a magnetic field

Solution:

When a proton and an electron having equal velocity are allowed to pass through a uniform magnetic field the proton and the electron experience equal and opposite force.
Correct Answer is `=>` (A) The proton and the electron experience equal and opposite force
Q 2326678571

A bar magnet is placed inside a uniform magnetic field. What does it experience?
NDA Paper 2 2008
(A)

A force

(B)

A torque

(C)

Both a force and a torque

(D)

Neither a force nor a torque

Solution:

If a bar magnet is placed in a uniform magnetic field, then North and South poles of the magnet will experience equal and opposite forces.
Correct Answer is `=>` (A) A force
Q 2336391272

Which one of the following does not affect the motion of a moving electron?
NDA Paper 2 2007
(A)

Electric field applied in the direction of motion

(B)

Magnetic field applied in the direction of motion

(C)

Electric field applied perpendicular to the direction of motion

(D)

Magnetic field applied perpendicular to the direction of motion

Solution:

Let us assume an electron moves in the magnetic field.
If magnetic field is in the direction of motion of electron i.e., `theta = 0`,
then no magnetic force will act on the motion of moving electron
Correct Answer is `=>` (B) Magnetic field applied in the direction of motion
Q 2346491373

Consider the following statements A body weighs less at the equator than at the poles because.
1. earth rotates about its axis.
2. the ice cap at the poles increases gravitational pull.
3. equatorial diameter is greater than the polar diameter.
4. of some unknown facts.
Which of the statements given above is/are not correct?
NDA Paper 2 2007
(A)

1 and 2

(B)

Only 3

(C)

1 and 3

(D)

Only 4

Solution:

We go from the equator towards the poles the value of g goes on increasing. Hence, body weighs less at the equator than at the poles and also equatorial diameter is greater than polar diameter.
Correct Answer is `=>` (B) Only 3
Q 2386891777

Which one of the following is the correct statement?
A fairly uniform magnetic field is produced
NDA Paper 2 2007
(A)

inside a horse-shoe magnet

(B)

inside a cylindrical conductor

(C)

inside a solenoid

(D)

between two parallel conductors

Solution:

Inside a solenoid, a fairly inform magnetic field is produced.
Correct Answer is `=>` (C) inside a solenoid
 
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