Moving Charges and Magnetic Effects Test

Result

Moving Charges and Magnetic Effects Test - 4

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Question 1
1 / -0

Lorentz Force generally refers to

A
force experienced by a charge due to combined action of electrical and magnetic fields is called the Lorentz force.

B
force experienced by a charge due to combined action of electrical fields

C
force experienced by a charge due to action of magnetic fields

D
force experienced by a charge due to combined action of electrical,magnetic field and gravitational field

Solution

The Lorentz Force is given by F = qE + q(v × B). It acts on a charged particle when it moves in the presence of electric as well as magnetic field.
Question 2
1 / -0

A 2 MeV proton is moving perpendicular to a uniform magnetic field of 2.5 T. The force on the proton is

A
8.52 10^-10 N

B
8.52 10^-11 N

C
7.84 10^-11 N

D
7.84 10^-12 N
Question 3
1 / -0

Two particles X and Y, having equal charges, after being accelerated through the same potential difference, enter a region of uniform magnetic field and describe circular paths of radii R₁ and R₂, respectively. The ratio of mass of X to that of Y is

A

B

C

D
Question 4
1 / -0

A particle of mass m and charge q moves with a constant velocity v along the positive x direction. It enters a region containing a uniform magnetic field B directed along the negative z direction, extending from x = a to x = b. The minimum value of v required so that the particle can just enter the region x > b, is

A
qbB/m

B
q(b – a)B/m

C
qaB/m

D
q(b + a)B/2m
Question 5
1 / -0

A straight section PQ of a circuit lies along the x–axis from x = – to x = and carries a current I. The magnetic field due to the section PQ at point x = + a will be

A
proportional to a

B
proportional to a²

C
proportional to

D
equal to zero
Question 6
1 / -0

Which of the following is most general charachteristic of Magnetic field

A
which of the following best describes the difference between electric and magnetic fields

B
The electric force acts in the direction perpendicular to electric field, whereas the magnetic force acts parallel to the magnetic field

C
The electric force acts on positive charges in the electric field, whereas the magnetic force acts on negative charges in the magnetic field

D
The electric force acts on negative charges in the electric field, whereas the magnetic force acts on positive charges in the magnetic field

Solution
Question 7
1 / -0

A conducting circular loop of radius r carries a current i. It is placed in a uniform magnetic field B such that B is perpendicular to the plane of the loop. The magnetic force acting on the loop is

A
irB

B
^₂_irB

C
zero

D
^_irB
Question 8
1 / -0

A wire is perpendicular to the plane of the paper. A ring of compass needles surrounds the wire in the plane of the paper with center of ring being the center of the wire. Initially there is no current in the wire. What happens after a steady dc current is established in the wire?

A
Nothing happens

B
The needles become parallel to each other

C
Some needles become parallel to each other while others are unaffected

D
The needles become tangential to the ring of which they are a part

Solution

The current carrying wire has a magnetic field around it and the lines of force are in the form of concentric circles with their centers on the wire.
Question 9
1 / -0

A charged particle is released from rest in a region of steady and uniform electric and magnetic fields, which are parallel to each other. The particle will move in a

A
straight line

B
circle

C
helix

D
cycloid
Question 10
1 / -0

A power line lies along the East-West direction and carries a current of 10 A. The force per unit length due to the earth's magnetic field of 10^–4 T is

A
10^–5 Nm^–1

B
10^–4 Nm^–1

C
10^–3 Nm^–1

D
10^–2Nm^–1
Question 11
1 / -0

A straight horizontal conducting rod of length 0.5 m and mass 50 g is suspended by two vertical wires at its ends. A current of 5.0 A is set up in the rod through the wires. What magnetic field should be set up normal to the conductor such that the tension in the wires is zero? (lgnore the mass of the wires and take g = 10 ms^-2.)

A
0.1 T

B
0.2 T

C
0.3 T

D
0.4 T
Question 12
1 / -0

An electron of charge e moves in a circular orbit of radius r around the nucleus at a frequency v. The magnetic moment associated with the orbital motion of the electron is

A
v e r²

B

C

D
Question 13
1 / -0

In the region around a moving charge, there is

A
electric field only

B
magnetic field only

C
neither electric field nor magnetic field

D
electric field as well as magnetic field
Question 14
1 / -0

If a wire of length L carrying a current I is bent into a circle, then the magnitude of magnetic field at the centre of the circle is

A

B

C

D
Question 15
1 / -0

direction of magnetic force on a positive charge moving in a magnetic field is given by

A
thumb rule

B
left hand rule

C
two hand rule

D
right hand rule

Solution
Question 16
1 / -0

A circular coil of radius r, having n number of turns and carrying a current I, produces magnetic field of magnitude B at its centre. B can be doubled by

A
keeping n unchanged and changing I to

B
changing n to and keeping I unchanged

C
changing n to 2n and I to 2I

D
keeping I unchanged and changing n to 2n
Question 17
1 / -0

A particle of charge q and mass m moves in a circular orbit of radius r with an angular speed . The ratio of the magnitude of its magnetic moment to that of its angular momentum depends on

A
and q

B
, q and m

C
q and m

D
and m
Question 18
1 / -0

A wire of length L metres carrying a current I amperes is bent in the form of a circle. The magnitude of the magnetic moment is

A

B

C

D
Question 19
1 / -0

Two particles, each of mass m and charge q, are attached to the two ends of a light rigid rod of length 2I. The rod is rotated at a constant angular speed about a perpendicular axis that passes through its centre. The ratio of the magnitude of the magnetic moment of the system to its angular momentum about the centre of the rod is

A

B

C

D
Question 20
1 / -0

Which of these equations is the correct expression for force on a charge in magnetic field

A

B

C

D

Solution