JEE Questions for Physics Moving Charges And Magnetism Quiz 3 - MCQExams.com

A current I ampere flows in the loop having circular arc of radius r subtending an angle θ as shown in fig. the magnetic field at the Centre O of the circle is.
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A particle with specific charge s is fired with a speed υ towards a wall at a distance d, perpendicular to the wall. What minimum magnetic field must exist in this region for the particle not to hit the wall?

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Field inside a solenoid is
  • Directly proportional to its length
  • Directly proportional to current
  • Inversely proportional to total number of turns
  • Inversely proportional to current
A circular coil of radius R carries an electric current. The magnetic field due to the coil at a point on the axis of the coil located at a distance r from the centre of the coil, such that r >> R, varies as

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Magnetic effect of current was dicovered by
  • Faraday
  • Oersted
  • Ampere
  • Bohr
The direction of magnetic lines of forces close to a straight conductor carrying current will be
  • Along the length of the conductor
  • Radially outward
  • Circular in a plane perpendicular to the conductor
  • Helical
The distance at which the magnetic field on axis as compared to the magnetic field at the centre of the coil carrying current I and radius R is 1/8, would be
  • R
  • √2 R
  • 2R
  • √3 R
A current i is passing through a straight conductor of infinite length. The magnetic field at a point situated at a distance R from the conductor is

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The earth\'s magnetic induction at certain point is 7 × 10–5 Wb/m2. This is to be annulled by the magnetic induction at the centre of a circular conducting loop of radius 5 cm. The required current in the loop is
  • 0.56 A
  • 5.6 A
  • 0.28 A
  • 2.8 A
A straight wire carrying a current 10 A is bent into a semicircular arc of radius 5 cm. The magnitude of magnetic field at the centre is
  • 1.5 × 10–5 T
  • 3.14 × 10–5 T
  • 6.28 × 10–5 Tq
  • 19.6 × 10–5 T
An electric current passes through a long straight wire. At a distance 5 cm from the wire, the magnetic field is B. The field at 20 cm from the wire would be
  • B/6
  • B/4
  • B/3
  • B/2
When a certain length of wire is turned into one circular loop, the magnetic induction at the centre of coil due to some current flowing is B0. If the same wire is turned into three loops to make a circular coil, the magnetic induction at the centre of this coil for the same current will be
  • B0
  • 9B0
  • 3B0
  • 27B0
The current in the windings on a toroid is 2.0 A. There are 400 turns and the mean circumferential length is 40 cm. If the inside magnetic field is 1.0 T, the relative permeability is near to
  • 100
  • 200
  • 300
  • 400
A long solenoid carrying a current produces a magnetic field B along its axis. If the current is doubled and the number of turns per cm is halved, the new value of the magnetic field is
  • B
  • 2B
  • 4B
  • B/2
The earth\'s magnetic field at a given point is 0.5 × 10–5 Wb-m–2. This field is to be annulled by magnetic induction at the center of a circular conducting loop of radius 5.0 cm. The current required to be flown in the loop is nearly
  • 0.2 A
  • 0.4 A
  • 4A
  • 40A
The magnetic moment of a current (i) carrying circular coil of radius (r) and number of turns (n) varies as
  • 1/r2
  • 1/r
  • r
  • r2
When the current flowing in a circular coil is doubled and the number of turns of the coil in it is halved, the magnetic field at its centre will become
  • Four times
  • Same
  • Half
  • Double
The field due to a long straight wire carrying a current I is proportional to
  • I
  • I3
  • √I
  • 1/I
A wire carrying current I and other carrying 2I in the same direction produces a magnetic field B at the mid point. What will be the field when 2I wire is switched off
  • B/2
  • 2B
  • B
  • 4B
Ampere\'s circuital law is equivalent to
  • Biot-Savart's law
  • Coulomb's law
  • Faraday's law
  • Kirchhoff's law

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  • Always zero
  • Never zero

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A strong magnetic field is applied on a stationary electron, then
  • The electron moves in the direction of the field
  • The electron moves in an opposite direction
  • The electron remains stationary
  • The electron starts spinning

Physics-Moving Charges and Magnetism-82360.png
  • T
  • 4T
  • 3T
  • 2T
In a cyclotron, the angular frequency of a charged particle is independent of
  • Mass
  • Speed
  • Charge
  • Magnetic field
Cyclotron is used to accelerate
  • Electrons
  • Neutrons
  • Positive ions
  • Negative ions
When a charged particle enters a uniform magnetic field, its kinetic energy
  • Remains constant
  • Increases
  • Decreases
  • Becomes zero
If cathode rays are projected at right angles to a magnetic field, their trajectory is
  • Ellipse
  • Circle
  • Parabola
  • None of these
A charged particle is released from rest in a region of steady uniform electric and magnetic field which are parallel to each other. The particle will move in a
  • Straight line
  • Circle
  • Helix
  • Cycloid
Electrons move at right angles to a magnetic field of 1.5 × 10–2 tesla with a speed of 6 × 107 m/s. If the specific charge of the electron is 1.7 × 1011 C/kg, the radius of the circular path will be
  • 2.9 cm
  • 3.9 cm
  • 2.35 cm
  • 3 cm
The radius of a circular loop is r and a current i is flowing in it. The equivalent magnetic moment will be
  • ir
  • 2πir
  • iπr2
  • 1/r2
A current carrying loop is placed in a uniform magnetic field. The torque acting on it does not depend upon
  • Shape of the loop
  • Area of the loop
  • Value of the current
  • Magnetic field
To make the field radial in a moving coil galvanometer
  • The number of turns in the coil is increased
  • Magnet is taken in the form of horse-shoe
  • Poles are cylindrically cut
  • Coil is wounded on aluminum frame
A current carrying circular loop is freely suspended by a long thread. The plane of the loop will point in the direction
  • Wherever left free
  • North-south
  • East-west
  • At 45° with the east-west direction
A current carrying small loop behaves like a small magnet. If A be its area and M its magnetic moment, the current in the loop will be
  • M/A
  • A/M
  • MA
  • A2M
Which is a vector quantity
  • Density
  • Magnetic flux
  • Intensity of magnetic field
  • Magnetic potential
An electron in a circular orbit of radius 0.05 nm performs 1016 revolutions per second. The magnetic moment due to this rotation of electron is (in A – m2 )
  • 2.16 × 10-23
  • 3.21 × 10-22
  • 3.21 × 10-24
  • 1.26 × 10-23
A long conducting wire carrying a current I is bent at 120° (see figure). The magnetic field B at a point P on the right bisector of bending angle at a distance d from the bend is (μ0 is the permeability of free space)
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A steady current flows in a long wire. It is bent into a circular loop of one turn and the magnetic field at the centre of the coil is B. If the same wire is bent into a circular loop of n turns, the magnetic field at the centre of the coil is

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A wire carrying current i is shaped as shown. Section AB is a quarter circle of radius r. The magnetic field is directed
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  • perpendicular to the plane of the paper and directed into the paper
  • an angle π/4 to the plane of the paper
  • along the bisector of the angle ACB away from AB
  • along the bisector of ACB towards AB
A steady current I flows along an infinitely long hollow cylindrical conductor of radius R. This cylinder is placed coaxially inside an infinite solenoid of radius 2R. The solenoid has n turns per unit length and carries a steady current I. Consider a point P at a distance r from the common axis. The correct statement (s) is (are)
  • In the region 0 < r < R, the magnetic field is non-zero
  • In the region R < r < 2R, the magnetic field is along the common axis
  • In the region R < r < 2R, the magnetic field is tangential to the circle of radius r, centered on the axis
  • In the region r > 2R, the magnetic field is non-zero
A current I flow in an infinitely long wire cross-section in the form of a semi-circular ring of radius R. The magnitude of the magnetic induction along its axis is

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A current of i ampere flows in a circular area of wire which subtends an angle of (3π/radian at its centre, whose radius is R. The magnetic induction B at the centre is
  • μ0i/R
  • μ0i/2R
  • 2μ0i/R
  • 3μ0i/8R
A current i is flowing through the loop. The direction of the current and the shape of the loop are as shown in the figure.
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PQ and RS are long parallel conductors separated by certain distance. M is the mid-point between them (see the figure). The net magnetic field at M is B. Now, the current 2 A is switched off. The field at M now becomes
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  • 2B
  • B

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  • 3B
Magnetic field at the centre of a circular coil of radius R due to i flowing through it is B. The magnetic field at a point along the axis at distance R from the centre is

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    Physics-Moving Charges and Magnetism-82405.png

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Two thick wires and two thin wires, all of same material and same length, form a square in three different ways P, Q and R as shown in the figure. With correct connections shown, the magnetic field due to the current flow, at the centre of the loop will be zero in case of
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  • Q and R
  • P only
  • P and Q
  • P and R
Two long straight wires are set parallel to each other. Each carries a current i in the opposite direction and the separation between them is 2R. The intensity of the magnetic field midway between them is
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  • zero
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  • 2

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A circular coil of wire consisting of 100 turns, each of radius 8.0 cm carries a current of 0.40 A. What is the magnitude of the magnetic field B at the centre of the coil?
  • π × 10-3 T
  • 2π × 10-4 T
  • π × 10-4 T
  • zero
A solenoid consists of 100 turns of wire and has a length of 10.0 cm. The magnetic field inside the solenoid when it carries a current of 0.500 A will be
  • 6.28 × 10-4 T
  • 6.28 × 10-5 T
  • 3.14 × 10-4 T
  • None of these
0:0:1


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