31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - NEET MCQ

# 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - NEET MCQ

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## 70 Questions MCQ Test Physics Class 12 - 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 for NEET 2024 is part of Physics Class 12 preparation. The 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 questions and answers have been prepared according to the NEET exam syllabus.The 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 MCQs are made for NEET 2024 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 below.
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31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 1

### The magnetic force acting on a charged particleof charge – 2μC in a magnetic field of 2T actingin y direction, when the particle velocity is  , is

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 1

The magnetic force acting on the char ged paraticle is given by

∴  Force is of 8N along – z-axis.

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 2

### Under the influence of a uniform magnetic field,a charged particle moves with constant speed vin a circle of radius R. The time period of rotationof the particle: [2009]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 2

The time period of the charged particle is
given by

Thus, time period is independent of both v and R.

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 3

### A thin ring of radius R meter has charge q coulomb uniformly spread on it. The ring rotates about its axis with a constant frequency of f revolutions/s. The value of magnetic induction in Wb/m2 at the centre of the ring is [2010]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 3

Current in the ring due to rotation,

Therefore, magnetic field at the centre of the ring is

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 4

A galvanometer has a coil of resistance 100 ohmand gives a full-scale deflection for 30 mAcurrent. It is to work as a voltmeter of 30 voltrange, the resistance required to be added willbe           [2010]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 4

Let the resistance to be added be R, then

30 = Ig(r + R)

= 1000 – 100 = 900Ω

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 5

A square current carrying loop is suspended in a uniform magnetic field acting in the plane of the loop. If the force on one arm of the loop is , the net force on the remaining three arms of the loop is

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 5

The force on the two arms parallel to the field is zero.

∴ Force on remaining arms = – F

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 6

A particle having a mass of 10–2 kg carries a charge of 5 × 10–C. The particle is given an initial horozontal velocity of 105 ms–1 in the presence of electric field   and magnetic field  . To  keep the particle moving in a horizontal direction, it is necessary that

(1)  should be perpendicular to the direction of velocity and should be along the direction of velocity.

(2) Both   and  should be along the direction of velocity.

(3) Both   and  are mutually perpendicular and perpendicular to the direction of velocity.

(4)  should be along the direction of velocity and should be perpendicular to the direction of velocity

Which one of the following pairs of statements is possible?

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 6

Case 1:- In figure 1 if FE​=FB​ ⇒ particle will always move in a straight line.(option (iii))
Case 2:- In figure 2 particle will always move in a straight line.(option (ii))

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 7

A closely wound solenoid of 2000 turns and areaof cross-section 1.5 × 10–4 m2 carries a currentof 2.0 A. It suspended through its centre andperpendicular to its length, allowing it to turn ina horizontal plane in a uniform magnetic field 5 ×10–2 tesla making an angle of 30° with the axis ofthe solenoid. The torque on the solenoid will be:

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 7

Torque on the solenoid is given by ζ = MB sinθ where θ is the angle between the magnetic field and the axis of solenoid.
M = niA
∴   ζ = niA B sin 30°

= 1.5 x 10-2 N-m

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 8

A current loop consists of two identical semicircular parts each of radius R, one lying in the x-y plane and the other in x-z plane. If the current in the loop is i., the resultant magnetic field due to the two semicircular parts at their common centre is

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 8

Magnetic fields due to the two parts at their common centre are respectively,

Resultant field =

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 9

A current carrying loop in the form of a right angle isosceles triangle ABC is placed in a uniform magnetic field acting along AB. If the magnetic force on the arm BC is F, what is the force on the arm AC?

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 9

Let a current i be flowing in the loop ABC in the direction shown in the figure. If the length of each of the sides AB and BC be x then

where B is the magnitude of the magnetic force.
The direction ofwill be in the direction perpendicular to the plane of the paper and going into it.
By Pythagorus theorem,

∴ Magnitude of force on AC

x  B sin 45°

The direction of the force on AC is perpendicular to the plane of the paper and going out of it. Hence, force on

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 10

A uniform electric field and uniform magneticfield are acting along the same direction in acertain region. If an electron is projected in theregion such that its velocity is pointed alongthe direction of fields, then the electron        [2011]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 10

are in same direction so that magnetic force on electron becomes zero, only electric force acts. But force on electron due to electric field is opposite to the direction of velocity.

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 11

A galvanometer of resistance, G is shunted by a resistance S ohm. To keep the main current in the circuit unchanged, the resistance to be put in series with the galvanometer is          [2011M]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 11

To keep the main current in the circuit unchanged, the resistance of the galvanometer should be equal to the net resistance.

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 12

A square loop, carrying a steady current I, is placed in a horizontal plane near a long straight conductor carrying a steady current I1 at a distance d from the conductor as shown in figure. The loop will experience    [2011M]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 12

and F3 and F4 are equal and opposite. Hence, the net attraction force will be towards the conductor.

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 13

Charge q is uniformly spread on a thin ring of radius R. The ring rotates about its axis with a uniform frequency f Hz. The magnitude of magnetic induction at the centre of the ring is        [2011M]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 13

When the ring rotates about its axis with a uniform frequency f Hz, the current flowing in the ring is

Magnetic field at the centre of the ring is

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 14

Two similar coils of radius R are lying concentrically with their planes at right angles to each other. The currents flowing in them are
I and 2 I, respectively. The resultant magnetic field induction at the centre will be:      [2012]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 14

The magnetic field, due the coil, carrying current I Ampere

The magnetic field due to the coil, carrying current 2I Ampere

The resultant B

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 15

An alternating electric field, of frequency v, is applied across the dees (radius = R) of a cyclotron that is being used to accelerate
protons (mass = m). The operating magnetic field (B) used in the cyclotron and the kinetic energy (K) of the proton beam, produced by it, are given by : [2012]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 15

Time period of cyclotron is

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 16

An α-particle moves in a circular path of radius   0.83 cm in the presence of a magnetic field of  0.25 Wb/m2. The de-Broglie wavelengthassociated with the particle will be :  [2012]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 16

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 17

A proton carrying 1 MeV kinetic energy ismoving in a circular path of radius R in uniformmagnetic field. What should be the energy of an α -particle to describe a circle of same radius inthe same field?    [2012M]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 17

According to the principal of circular motion in a magnetic field

but    R = Rα (given)

Thus K = K' = 1 MeV

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 18

A current loop in a magnetic field [NEET 2013]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 18

A current loop in a magnetic field is in equilibrium in two orientations one is stable and another unstable.

= M B sinθ

Do not experience a torque in some orientations Hence option (c) is correct.

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 19

When a proton is released from rest in a room, it starts with an initial acceleration a0 towards west. When it is projected towards north with a speed v0 it moves with an initial acceleration 3a0 towards west. The electric and magnetic fields in the room are respectively      [NEET 2013]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 19

When moves with an acceleration a0 towards west, electric field

When moves with an acceleration 3a0 towards east, magnetic field

(downward)

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 20

A long straight wire carries a certain current and produces a magnetic field of  at a perpendicular distance of 5 cm from the wire. An electron situated at 5 cm from the wire moves with a velocity 107 m/s towards the wire along perpendicular to it. The force experienced by the electron will be
(charge on electron =1.6 × 10–19 C)

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 20

Given: Magnetic field B = 2 × 10–4 weber/m2
Velocity of electron, v = 107  m/s
Lorentz force F = qvB sinθ = 1.6 × 10–19 × 107 × 2 × 10–4 (∵ θ = 90°)
= 3.2 × 10–16 N

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 21

When a proton is accelerated through 1 V, thenits kinetic energy will be [1999]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 21

Potential difference (V) = 1V, K.E. acquired = qV = 1.6 × 10–19 × 1
= 1.6 × 10–19  joules = 1 eV

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 22

If a long hollow copper pipe carries a current,then magnetic field is produced [1999]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 22

Inside a hollow pipe carrying current, the magnetic field is zero, since according to Ampere's law, Bi. 2πr = μ0 × 0 ⇒ Bi = 0.
But for external points, the current behaves as if it was concentrated at the axis only; so, outside,Thus, the magnetic field is produced outside the pipe only.

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 23

Two long parallel wires P and Q are both perpendicular to the plane of the paper with distance of 5 m between them. If P and Q carry currents of 2.5 amp and 5 amp respectively in the same direction, then the magnetic field at a point half-way between the wires is       [2000]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 23

When the current flows in both wires in the same direction then magnetic field at half way due to the wire P,

(where I1= 2.5 amp) The direction of  is downward

Magnetic field at half way due to wire Q

[where I2 = 2.5amp.]

Net magnetic field at half way

Hence, net magnetic field at midpoint

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 24

A proton moving with a velocity 3 × 105 m/senters a magnetic field of 0.3 tesla at an angle of30º with the field. The radius of curvature of itspath will be (e/m for proton = 108 C/kg)         [2000]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 24

= 0.5 x 10 -2m = 0.5cm

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 25

In a certain region of space electric field and magnetic field are perpendicular to each other and an electron enters in region perpendicular to the direction of and both and moves undeflected, then velocity of electron is [2001]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 25

Electron moves undeflected if force exerted due to electric field is equal to force due to magnetic field.

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 26

A charged particle of charge q and mass m enters perpendicularly in a magnetic field  . Kinetic energy of the particle is E; then frequency of rotation is [2001]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 26

For circular path in magnetic field, mrω2 = qvB

∴  If v is frequency of roatation, then

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 27

A galvanometer can be converted into avoltmeter by connecting           [2002]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 27

A galvanometer can be converted in to a voltmeter by connecting  the high ressistance in series with the galvanometer so that only a small amount of current passes through it.

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 28

A wire carries a current. Maintaining the samecurrent it is bent first to form a circular plane coil ofone turn which produces a magnetic field B at thecentre of the coil. The same length is now bentmore sharply to give a double loop of smaller radius.The magnetic field at the centre of the double loop,caused by the same current is          [2002]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 28

Let I be current and l be the length of the wire.
For Ist case :where
2πr = l and n = 1

For IInd Case :

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 29

A particle having charge q moves with a velocity  through a region in which both an electric field  and a magnetic field  are present .The force on the particle is           [2002]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 29

Force due to electric field =

Force due to magnetic field =

Net force experienced =

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 30

A charged particle moves through a magneticfield in a direction perpendicular to it. Then the         [2003]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 30

Magnetic for ce acts perpendicular to the velocity. Hence speed remains constant.

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 31

A long solenoid carrying a current produces amagnetic field B along its axis. If the current isdouble and the number of turns per cm is halved,the new value of the magnetic field is     [2003]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 31

B = μ0ni

⇒ B1 = B

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 32

A galvanometer acting as a voltmeter will have            [2004]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 32

A high resistance is connected in series so that less current passes through voltmeter.

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 33

A galvanometer of 50 ohm resistance has 25 divisions. A current of 4 × 10–4 ampere gives adeflection of one per division. To convert thisgalvanometer into a voltmeter having a rangeof 25 volts, it should be connected with aresistance of [2004]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 33

Rg = 50Ω, Ig = 25 × 4 × 10–AΩ = 10–2 A
Range of V = 25 volts V = Ig(Re + Rg)

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 34

An electron moves in a circular orbit with a uniform speed v. It produces a magnetic field B at the centre of the circle. The radius of the circle is proportional to      [2005]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 34

The magnetic field produce by moving electron in circular path

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 35

A very long straight wire carries a current I. At the instant when a charge + Q at point P has velocity , as shown, the force on the charge is

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 35

The direction of

∴  The magnetic  force

is along OY.

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 36

When a charged particle moving with velocity   is subjected to a magnetic field of induction   the force on it is non-zero. This implies that

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 36

Force on a particle moving with velocity v in a magnetic field  B is

If angle between is either zero or 180º, then value of F will be zero as cross product of will be zero.
So option (b) is correct.

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 37

Two circular coils 1 and 2 are made from the samewire but the radius of the 1st coil is twice that ofthe 2nd coil. What potential difference in voltsshould be applied across them so that themagnetic field at their centres is the same [2006]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 37

If R1 & R2 be the radius of the circular wires,

If same potential is applied on them, current in Ist will be half that in the later. If V potential is applied on them, current in them

Now magnetic field at the centre of circular

coil,

For first wire, field B1

For second wire, field B2  =

Given B1 = B2 The given data do not provide any required result. There is a mistake in the framing of the question.

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 38

A beam of electron passes undeflected throughmutually perpendicular electric and magnetic fields.If the electric field is switched off, and the samemagnetic field is maintained, the electrons move  [2007]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 38

If the electric field is switched off, and the same magnetic field is maintained, the electrons move in a circular orbit and electron will travel a magnetic field ⊥ to its velocity..

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 39

In a mass spectrometer used for measuring the masses of ions, the ions are initially accelerated by an electric potential V and then made to describe semicircular path of radius R using a magnetic field B. If V and B are kept constant, the ratio will be proportional to

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 39

In mass spectro meter, when ions are accelerated through potential V

..........(i)

As the magnetic field curves the path of the ions in a semicircular orbit

.......... (ii)

Substituting (ii) in (i)

Since V and B are constants,

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 40

Under the influence of a uniform magnetic fielda charged particle is moving in a circle of radiusR with constant speed v. The time period of themotion        [2007]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 40

When a test charge q0 enters a magnetic fielddirected along z-axis, with a velocity  making angles d with the z-axis. The time period of the motion is independent of R and v.

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 41

A closed loop PQRS carrying a current is placed in a uniform magnetic field. If the magnetic forces on segments PS, SR, and RQ are F1 , F2 and F3 respectively and are in the plane of the paper and along the directions shown, the force on the segment QP is       [2008]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 41

According to the figure the magnitude of force on the segment QM is F3 –F1 and PM is F2.

Therefore, the magnitude of the force on segment PQ is

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 42

A particle of mass m, charge Q and kinetic energyT enters a transverse uniform magnetic field ofinduction . After 3 seconds, the kinetic energyof the particle will be: [2008]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 42

When a charged particle enters a transverse magnetic field it traverse a circular path. Its kinetic energy remains constant.

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 43

A circular disc of radius 0.2 meter is placed in a uniform magnetic field of induction   in such a way that its axis makes an angle of 60° with . The magnetic flux linked with the disc is:        [2008]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 43

Here,

θ = 60°
Area normal to the plane of the disc

Flux = B × normal area

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 44

A galvanometer having a coil resistance of 60 Ωshows full scale deflection when a current of 1.0amp passes through it. It can be convertedinto an ammeter to read currents upto 5.0 amp by         [2009]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 44

G = 60Ω, Ig=1.0A, I=5A.

Let S be the shunt resistance connected in parallel to galvanometer IgG = (I – Ig) S,

Thus by putting 15Ω in parallel, the galvanometer can be converted into an ammeter.

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 45

A charged paritcle (charge q) is moving in a circleof radius R with uniform speed v. The associatedmagnetic moment μ is given by [2007]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 45

Magnetic moment, m = IA

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 46

A current carrying coil is subjected to a uniformmagnetic field. The coil will orient so that itsplane becomes [1988]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 46

The plane of coil will orient itself so that area vector aligns itself along the magnetic field.
So, the plane will orient perpendicular to the magnetic field.

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 47

Tesla is the unit of               [1988]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 47

Tesla is the unit of magnetic field.

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 48

Energy in a current carrying coil is stored in theform of             [1989]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 48

Energy is stored in magnetic field.

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 49

The total charge induced in a conducting loopwhen it is moved in a magnetic field depends on         [1990]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 49

Total charge induced =

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 50

The magnetic induction at a point P which is at adistance of 4 cm from a long current carryingwire is 10–3 T. The field of induction at a distance12 cm from the current will be [1990]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 50

As the distance is increased to three times, the magnetic induction reduces to one third.
Hence,  tesla = 3.33 x 10-4 tesla

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 51

A deuteron of kinetic energy 50 keV is describinga circular orbit of radius 0.5 metre in a planeperpendicular to the magnetic field B. The kineticenergy of the proton that describes a circularorbit of radius 0.5 metre in the same plane withthe same B is        [1991]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 51

For a charged particle orbiting in a circular path in a magnetic field

or, mv2 = Bqvr

Also,

For deuteron,

For proton,

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 52

A uniform magnetic field acts at right angles tothe direction of motion of electron. As a result,the electron moves in a circular path of radius2cm. If the speed of electron is doubled, thenthe radius of the circular path will be [1991]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 52

As v is doubled, the radius also becomes double. Hence, radius = 2 × 2 = 4 cm

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 53

The magnetic field at a distance r from a longwire carrying current i is 0.4 tesla. The magneticfield at a distance 2r is                [1992]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 53

When r is doubled, the magnetic field becomes half, i.e., now the magnetic field will be 0.2 T.

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 54

A straight wire of length 0.5 m that is carrying a current of 1.2 A is placed in a uniform magnetic field of induction 2T, and the magnetic field is perpendicular to the length of the wire. What is the force of the wire?

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 54

F = Biℓ = 2 ×1.2 × 0.5 = 1.2 N

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 55

To convert a galvanometer into an ammeter, oneneeds to connect a        [1992]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 55

To convert a galvanometer into an ammeter, one needs to connect a low resistance in parallel so that maximum current passes through the shunt wire and ammeter remains protected

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 56

A coil carrying electric current is placed inuniform magnetic field, then         [1993]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 56

A current carrying coil has magnetic dipole moment. Hence, a torque  acts on it in magnetic field.

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 57

A charge moving with velocity v in X-directionis subjected to a field of magnetic induction innegative X-direction. As a result, the charge will              [1993]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 57

The force acting on a charged particle in magnetic field is given by

When angle between v and B is 180°, F = 0

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 58

An electron enters a region where magnetic field(B) and electric field (E) are mutually perpendicular,then        [1994]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 58

When the deflection produced by electric field is equal to the deflection produced by magnetic field, then the electron can go undeflected.

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 59

A straight wire of diameter 0.5 mm carrying acurrent of 1 A is replaced by another wire of 1mm diameter carrying same current. The strengthof magnetic field far away is          [1995, 97, 99]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 59

and so it is independent of thickness.
The current is same in both the wires, hence magnetic field induced will be same.

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 60

At what distance from a long straight wirecarrying a current of 12 A will the magnetic fieldbe equal to 3×10-6Wb /m2 ?        [1995]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 60

Current (I) = 12 A and magnetic field (B) = 3 × 10–5 Wb/m2. Consider magnetic fieldat distance r..

Magnetic field ,

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 61

The magnetic field  due to a small element (dℓ ) at a distance  and element carrying current i is           [1996]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 61

According to Biot Savart law,

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 62

A 10 eV electron is circulating in a plane at rightangles to a uniform field at magnetic induction10– 4 Wb/m2 (= 1.0 gauss). The orbital radius ofthe electron is [1996]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 62

K.E. of electron = 10 eV

= 10 x 1.6 x 10 -19

⇒ v2 = 3.52 × 1012 ⇒ v = 1.88 × 106 m

Also, we know that for circular motion

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 63

Two equal electric currents are flowing perpendicular to each other as shown in the figure. AB and CD are perpendicular to each other and symmetrically placed with respect to the current flow. Where do we expect the resultant magnetic field to be zero? [1996]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 63

Net magnetic field on AB is zero because magnetic field due to both current carrying wires is equal in magnitude but opposite in direction.

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 64

A beam of electrons is moving with constantvelocity in a region having simultaneousperpendicular electric and magnetic fields ofstrength 20 Vm–1 and 0.5 T respectively at rightangles to the direction of motion of the electrons.Then the velocity of electrons must be         [1996]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 64

The electron moves with constant velocity without deflection. Hence, force due to magnetic field is equal and opposite to force due to electric field.

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 65

A galvanometer of resistance 20 Ω gives fullscale deflection with a current of 0.004 A. Toconvert it into an ammeter of range 1 A, therequired shunt resistance should be          [1996]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 65

Maximum current which can pass through galvanometer,  Ig = 0.004A

Let R be the resistance of shunt.
We know potential drop across AB = Potential drop across CD R (I – Ig) = Ig (20)
⇒ R (1 – 0.004) = 0.004 × 20 ⇒ R = 0.08Ω

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 66

A positively charged particle moving due eastenters a region of uniform magnetic field directedvertically upwards. The particle will      [1997]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 66

In a perpendicular magnetic field, the path of a charged particle is a circle, and the magnetic field does not cause any change in energy.

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 67

Two long parallel wires are at a distance of 1metre. Both of them carry one ampere of current.The force of attraction per unit length betweenthe two wires is [1998]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 67

= 2 × 10–7 N/m. [This relates to the definition of ampere]

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 68

A galvanometer having a resistance of 8 ohmsis shunted by a wire of resistance 2 ohms. If thetotal current is 1 amp, the part of it passingthrough the shunt will be          [1998]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 68

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 69

A coil of one turn is made of a wire of certainlength and then from the same length a coil oftwo turns is made. If the same current is passedin both the cases, then the ratio of the magneticinductions at their centres will be [1998]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 69

Let ℓ be length of wire.
Ist case : ℓ =2πr

2nd Case : ℓ = 2(2πr')

using (1) (where n = 2)

31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 70

Magnetic field intensity at the centre of a coil of50 turns, radius 0.5 m and carrying a current of 2A is       [1999]

Detailed Solution for 31 Year NEET Previous Year Questions: Moving Charges & Magnetism - 1 - Question 70

We know that magnetic field at the centre of circular coil,

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