Charges & Magnetism Test

Result

Charges & Magnetism Test - 5

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Question 1
1 / -0

Ratio of magnetic force F_m and electric force F_e acting on a charge getting undeflected through the field is

A
E/B

B
B/E

C
1

D
0

Solution

if the particle is undeflected, then the magnetic force equals the electric force:
q x v x B=q x E
B is the magnitude of the magnetic field
E is the magnitude of the electric field
v is the magnitude of the velocity of the particle.
If the forces are equal then:
v=E/B
For undeflected v=1
E/B=1
Question 2
1 / -0

Time taken by an ion to describe a semicircular path, in a cyclotron

A
Depends upon the electric field.

B
depends upon the radius of the circular path.

C
depends upon speed of ion.

D
is constant.

Solution

We also know for a circular motion time period = 2πm/qb as the charge in question has. Constant q, mass is also constant, b is also constant thus time period for semicircular path is constant.
Question 3
1 / -0

If a charged particle goes undeflected in a region containing electric and magnetic fields. Select all of the following statements that must be true for this.
1. must be perpendicular to
2. must be perpendicular to
3. must be perpendicular to
4. E must be equal to vB

A
1 and 2 only

B
1 only

C
1 and 3 only

D
2 only

Solution

If a charged particle goes unaccelerated in a region containing
electric and magnetic fields,
Question 4
1 / -0

The dipole moment of a current loop is independent of:

A
magnetic field of the loop.

B
current in the loop

C
area of the loop

D
number of turns

Solution

Dipole moment of a current loop
M=N ×I × A
So, it is dependent on current in the loop, number of turns and area of the loop.
It is independent of the magnetic field in which it is situated.
Question 5
1 / -0

If cathode rays are projected at right angles to a magnetic field, their trajectory is

A
Ellipse

B
Circle

C
Parabola

D
None of these

Solution

The magnetic force acts perpendicular to the velocity of the particle. This causes circular motion. In the magnetic field the speed and kinetic energy of the particle remain constant, but the direction is altered at each instant by the perpendicular magnetic force.