Download Moving Charges and Magnetism

(Q.1) What is the force between two straight conductors if they carry current in
opposite direction?
( 1 mark )
View Answer
Circular loop of a wire and a long straight wire carry
currents Ic and Ie, respectively as shown in figure. Assuming
that these are placed in the same plane, the magnetic fields
will be zero at the centre of the loop when the separation H is
:
(Q.2)
( 1 mark )
(A)
(B)
(C)
(D)
View Answer
A current carrying loop is placed in a uniform magnetic
field. The torque acting on it, does not depend upon
(A) Shape of the loop
(B) Area of the loop
(C) Value of the current
(D) Magnetic field
(Q.3)
( 1 mark )
View Answer
A toroid has a core of inner radius 20 cm and outer
radius 22 cm around which 4200 turns of a wire are wound.
If the current in the wire is 10 A, what is the magnetic field
inside the core of toroid.
(A) 0.4T
(B) 0.2T
(C) 0.04T
(D) 0.02T
(Q.4)
( 1 mark )
View Answer
In cyclotron the charged particle may be accelerated
upto energies
(Q.5)
( 1 mark )
(A) Several eV
(B) MeV
(C) BeV
(D) Kev
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Four wires, each of length 2.0 m, are bent into four loops
P, Q, R and S and then suspended in a uniform magnetic field.
If the same current is passed in each, then the torque will be
maximum on the loop
(Q.6)
( 1 mark )
(A) P
(B) Q
(C) R
(D) S
View Answer
A galvanometer can be converted into an ammeter by
using
(Q.7)
( 1 mark )
(A) Low resistance in series
(B) Low resistance in parallel
(C) High resistance in series
(D) High resistance in parallel
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A magnetic field is present, the direction of which is
perpendicular to the plane of the paper from the top to
bottom. An electron is projected into the field in the plane of
( 1 mark )
paper with a constant velocity. Looking in the initial direction
of motion of the electron, as it enters the magnetic field, it
would
(A) Move perpendicular to the plane of the paper on a circular path upwards
(B) Move perpendicular to the plane of the paper on a circular path towards right
(C) Move in the plane of the paper on a circular path towards the left
(D) Move perpendicular to the plane of the paper on a circular path downwards.
(Q.8)
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In a mass spectrograph, an ion x of mass number 24 and
charge + e and another ion y of mass 22 and charge + 2e
( 1 mark )
enter in a perpendicular magnetic field with the same
velocity. The ratio for the radii of their circular path in the
field will be
(A) 24/11
(B) 11/24
(C) 22/11
(D) 11/22
(Q.9)
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Two parallel wires are carrying electric currents of
equal magnitude and in the same direction. They exert
(A) An attractive force on each other
(B) A repulsive force on each other
(C) No force on each other
(D) None of these
(Q.10)
( 1 mark )
View Answer
A positive charged particle is moving with velocity v
enters into a region of space having a constant magnetic
( 1 mark )
induction B. The particle will experience the largest deflection
force when the angle between the vector A and B is
(A) 0°
(B) 45°
(C) 90°
(D) 180°
(Q.11)
View Answer
A very long straight wire carries a current I. At the
instant when a charge + Q at point P has velocity v , as
shown, the force on the charge is
(Q.12)
( 1 mark )
(A) Along OY
(B) Opposite to OY
(C) Along OX
(D) Opposite to OX
View Answer
Two long parallel wires are at a distance of 1 metre.
Both of them carry one ampere of current. The force of
attraction per unit length between the two wires is
(Q.13)
( 1 mark )
(A) 2 × 10–7 N/m
(B) 2 × 10–8 N/m
(C) 5 × 10–8 N/m
(D) 10–7 N/m
View Answer
Two circular, similar, coaxial loops carry equal current
in the same direction as shown in figure. If the loops are
brought nearer, what will happen?
(Q.14)
( 1 mark )
(A) Current will increase in each loop
(B) Current will decrease in each loop
(C) Current will remain same in each loop
(D) Current will increase in one and decrease in the other
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A charge particle enters a magnetic field at an angle of
45° with the magnetic field. The path of the particle will be
(A) Helical
(B) An ellipse
(C) A circle
(D) A straight line
(Q.15)
( 1 mark )
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An infinite long straight conductor is bent in the shape
shown in fig. It carries a current i amp and the radius of
circular loop is r m. Then the magnetic induction at the centre
of the circular loop will be
(Q.16)
( 1 mark )
(A)
(B)
(C) Zero
(D) None of these
View Answer
A direct current flows through a solenoid, entering in
an anticlockwise sense at the end A. This solenoid, made to
float on still water will
(A) Have the end A point towards north
(B) Have the end A point towards south
(C) Stay in any point towards south
(D) Move in a straight line with constant velocity
(Q.17)
( 1 mark )
View Answer
A solenoid of 1.5 metre length and 4.0 cm diameter
possesses 10 turns per cm. A current of 5 ampere is flowing
through it. The magnetic field at the axis inside the solenoid
is :
(A) 2 × 103 Tesla
(B) 2 × 106 Tesla
(C) 4 × 103 Gauss
(D) 2 × 103 Gauss
(Q.18)
View Answer
( 1 mark )
(Q.19)
The work done by a magnetic field, on a moving charge
is
(A) Zero because
acts parallel to
(B) Positive because
(C) Zero because
( 1 mark )
acts perpendicular to
acts perpendicular to
(D) Negative because
View Answer
acts parallel to
A positively charged particle moving due east enters a
region of uniform magnetic field directed vertically upwards.
This particle will
(A) Get deflected in vertically upward direction
(B) Move in circular path with an increased speed
(Q.20)
( 1 mark )
(C) Move in a circular path with decreased speed
(D) Move in a circular path with uniform speed
View Answer
If a long hollow copper pipe carries a direct current, the
( 1 mark )
magnetic field associated with the current will be
(A) Only inside the pipe
(B) Only outside the pipe
(Q.21)
(C) Neither inside nor outside the pipe
(D) Both inside and outside the pipe
View Answer
A proton of mass 1.67 × 10–27 kg and charge 1.6 × 10–19
C is projected with a speed of 2 × 106ms–1 at an angle of 60º
( 1 mark )
to the X-axis. If a uniform magnetic field of 0.104 tesla is
applied along Y-axis, the path of proton is
(A) A circle of radius = 0.2 m and time period = 2p × 10–7 s
(Q.22)
(B) A circle of radius = 0.1 m and time period = 2p × 10–7 s
(C) A helix of radius = 0.1 m and time period = 2p × 10–7 s
(D) A helix of radius = 0.2 m and time period = 2p × 10–7 s
View Answer
A length of wire carries a steady current. It is bent first
to form a circular plane coil of one turn. The same length is
now bent more sharply to give a double loop of smaller
radius. The magnetic field at the centre caused by the same
current is
(A) Quarter of its first value
(B) Unaltered
(C) Four times of its first value
(Q.23)
( 1 mark )
(D) Half of its first value
View Answer
Which of the following graphs, shows the variation of
magnetic induction B with distance r from a long wire
carrying a current?
(Q.24)
(A)
(B)
(C)
( 1 mark )
(D)
View Answer
A cell is connected between two points of a uniformly
thick circular conductor. i1 and i2 are the currents flowing in
two parts of the circular conductor of radius a. The magnetic
field at the centre of the loop will be
(A) zero
(Q.25)
( 1 mark )
(B)
(C)
(D)
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(Q.26) What is the resistance of an ideal ammeter?
( 1 mark )
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(Q.27) Name the force which is experienced by the moving charged particles in
the magnetic field.
( 1 mark )
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(Q.28) When will be the force experienced by a moving charge in a magnetic field
maximum?
( 1 mark )
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(Q.29) What happens to the speed and kinetic energy of a particle when it is
projected perpendicular to the magnetic field.
( 1 mark )
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(Q.30) How ammeter and voltmeter is connected in a circuit?
( 1 mark )
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(Q.31) Which will experience greater torque? A circular loop or a square loop
having same current and placed in a uniform magnetic field.
( 1 mark )
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(Q.32) On what principle does cyclotron works?
( 1 mark )
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(Q.33) Astraight wire of mass 200 g and length 4.9 m carries a current of 2 A. It
is suspended in mid air by a uniform horizontal magnetic field B. What is the
magnitude of the magnetic field?
( 1 mark )
(A) 0.3
(B) 0.2
(C) 2
(D) 0.4
View Answer
(Q.34) Circular loop of a wire and a long straight wire carry currents Icand
Ie,
respectively as shown in figure. Assuming that these are
placed in the same plane, the magnetic fields will be zero at
the centre of the loop when the separation H is :
( 1 mark )
(A)
(B)
(C)
(D)
View Answer
(Q.35) What is the conductance of a conductor of resistance 5 milli ohm?
( 1 mark )
(A) 200 mho
(B) 100 mho
(C) 500 mho
(D) none of these
View Answer
(Q.36) A short bar magnet is placed with its north pole pointing south. The
natural point is 10 cm away from the center of the magnet. If H=0.4 gauss, what
is the magnetic moment of the magnet.
( 1 mark )
(A) 0.2 A m2
(B) 2 A m2
(C) 20 A m2
(D) None of these
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(Q.37) Define Biot-Savart Law.
( 2 Marks )
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(Q.38) What is magnetic effect of current?
( 2 Marks )
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(Q.39) A galvanometer has a resistance of 55 ohms. It gives full-scale deflection
by a current of 10 milliamperes. What resistance must be connected across it to
enable it to read 1 ampere?
( 2 Marks )
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(Q.40) What is the force on a charged particles when it is moving at right angle to
the applied magnetic field?
( 2 Marks )
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(Q.41) What is the force between two parallel conductors carrying current?
( 2 Marks )
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(Q.42) Why a galvanometer cannot be used as an ammeter directly?
( 2 Marks )
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(Q.43) What is the magnitude of magnetic field at a distance R-from a long
straight wire carrying a current I?
( 2 Marks )
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(Q.44) Define Lorentz force?
( 3 Marks )
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(Q.45) Define Ampere’s circuital law?
( 3 Marks )
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(Q.46) What is cyclotron frequency?
( 3 Marks )
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(Q.47) Two straight wires A and B of length 20 m and 32 m and carrying currents
4 A and 5 A respectively in same directions, are parallel to each other 4 m
apart.Find the force on the 10 m long section of the wire B near its centre.
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( 3 Marks )
A straight conducting rod of length .06m and mass 30g
is suspended by two vertical wires at its ends. A current of 1
A is set up in the rod. Find
(a) what magnetic field should be set up normal to the
conductor so that tension in the wire is zero?
(b) what will be the total tension in the wire if the direction
of the current is reversed
(Q.48)
( 5 Marks )
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(Q.49) A very long wire carrying a current i=10 A is bent at right angles.Find the
magnetic induction at a point lying on a perpendicular to the wires drawn through
the point of bending, at a distance l= 30 cm from it.
( 5 Marks )
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(Q.50) In an ammeter, 0.5% of main current pass through galvanometer. If
resistance of galvanometer is G, what will be the resistance of ammeter?
( 5 Marks )
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(Q.51) The plane of a rectangular loop of wire of sides 0.05m and 0.08m is placed
in a uniform magnetic field of induction 1.5 x 10-2 texla. A current of 10.0 amp
flows through the loop. The plane of the coils are normal to the lines of induction.
what is the torque acting on it?
( 5 Marks )
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(Q.52) Derive the formula for magnetic field on the axis of a circular current
loop?
( 5 Marks )
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(Q.53) Mention the principle and construction of moving coil galvanometer?
( 5 Marks )
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(Q.54) Differentiate between a solenoid and a toroid.
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( 5 Marks )