Moving Charges and Magnetism Test

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Moving Charges and Magnetism Test - 31

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Weekly Quiz Competition

Question 1
1 / -0

A electron with kinetic energy $k$ enters a region (i) uniform magnetic field (ii) non-uniform magnetic field and comes out with kinetic energy $k_1$ and $k_2$ respectively. What is relation between $k_1, k_2$ and $k$ ?

A
$K_1 > K_2 > K$

B
$K_1 = K_2 > K$

C
$K_1 = K_2 = K$

D
$K_1 < K_2 < K$

Solution

Any type of magnetic field can not change kinetic energy of charged particle. So $K_1 = K-2 = K$
Question 2
1 / -0

Which of these particles will have minimum frequency of revolution when projected with the same velocity perpendicular to a magnetic field ?

A
proton

B
$\alpha$ partcle

C
neutron

D
electron

Solution

When a charged particle of charge 'q' and man 'm' is projected to a
magnetic field in perpendicular to $\vec{B}$ , it revolves with a frequency of:-
$V=\dfrac{Bq}{2\pi m}$
Hence , a large charge /man (q/m) ratio means higher frequency
out of $4$ option an electrons has highest q/m ratio ,using to its low man
$\therefore$ The electron will have highest frequency
Question 3
1 / -0

Cathode rays and canal rays produced in a certain discharge tube are deflected in the same direction if

A
A magnetic field is applied normally

B
An electric field is applied normally

C
An electric field is applied tangentially

D
A magnetic field is applied tangentially

Solution

In discharge tube cathode rays (a beam of negative particles) and canal rays (positive rays) moves opposite to each other. They will experience a magnetic force in the same direction, if a normal magnetic field is switched on
Question 4
1 / -0

When an electron moves through a magnetic field, its speed will

A
decrease.

B
increase.

C
remain the same.

D
increase first and then decrease.

Solution

The work done by magnetic force on any moving charge particle is zero because magnetic force acts perpendicular to the direction of motion. Therefore speed will remain same.
Question 5
1 / -0

An electron and a proton are injected into a uniform magnetic field at right angle to its direction with the same momentum. Then

A
electrons path isless curved than protons path

B
protons path will be less curved than electrons

path

C
the paths of both will be equally curved

D
both the trajectories will be straight

Solution

R = $\dfrac{mv}{QB} = \dfrac{P}{QB}$ [ P is same]
Q and B are same in magnitude in case of e and p their path will be equally curved
Question 6
1 / -0

An electron is not deflected on passing through a certain region, because

A
there is magnetic field in that region and the electron enters into it in any direction.

B
there may be magnetic field but the velocity of electron may be parallel to the direction of magnetic field

C
electron is a chargeless particle

D
there is electric field and the electron enters into it in any direction.

Solution

only B is possible because $\vec{B} \parallel \vec{v}$
Question 7
1 / -0

A $\beta -$ particle enters a magnetic field making an angle of $45^{o}$ with the field lines. The path of the particle is

A
circular

B
elliptical

C
spiral

D
a straight line

Solution

the $v_x = \dfrac{v}{\sqrt 2}$ will be responsible for circular motion and $v_y$ will take it in $+Y$ direction thus making it a spiral path
Question 8
1 / -0

An electron enters a magnetic field with a speed of $10^{8} cm/s$ . The particle experiences a force due to the magnetic field and the speed of the electron

A
will decrease

B
will increase

C
will remain constant

D
may in crease or decrease

Solution

A particle travelling perpendicular to a magnetic field would experience a force given by $F=q(\vec{v}\times \vec{B})$ .
This force, thus, acts perpendicular to the direction of motion of electron. Hence it only changes the direction of electron but not the speed of electron perpendicular to the direction of motion. This force would cause a constant centripetal acceleration. Thus the speed of electron does not change at all.
Question 9
1 / -0

An electron is projected into a magnetic field along the lines of force. Then

A
there will be no effect on its motion

B
the electron will travel along a circle and its speed remains unchanged

C
the electron will follow the path of a parabola and its speed will increase

D
the velocity will increase in magnitude but its direction will remain unchanged.

Solution

if $\vec{v} \parallel \vec{B}$
then $\theta$ = 0
$\implies \vec{F_B}$ = 0
Question 10
1 / -0

When a charged particle moves through a magnetic field, the quantity which is not affected in the magnetic field is:

A
particle velocity

B
particle acceleration

C
linear momentum of the particle

D
kinetic energy of the particle

Solution

Magnetic field does zero work on moving charged particles. Therefore, kinetic energy of particle remains constant.

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Moving Charges and Magnetism Test - 31

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Moving Charges and Magnetism Test - 31

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Question 1

K1>K2>KK_1 > K_2 > KK1​>K2​>K

K1=K2>KK_1 = K_2 > KK1​=K2​>K

K1=K2=KK_1 = K_2 = KK1​=K2​=K

K1<K2<KK_1 < K_2 < KK1​<K2​<K

Solution

Question 2

proton

α\alphaα partcle

neutron

electron

Solution

Question 3

A magnetic field is applied normally

An electric field is applied normally

An electric field is applied tangentially

A magnetic field is applied tangentially

Solution

Question 4

decrease.

increase.

remain the same.

increase first and then decrease.

Solution

Question 5

electrons path isless curved than protons path

protons path will be less curved than electronspath

the paths of both will be equally curved

both the trajectories will be straight

Solution

Question 6

there is magnetic field in that region and the electron enters into it in any direction.

there may be magnetic field but the velocity of electron may be parallel to the direction of magnetic field

electron is a chargeless particle

there is electric field and the electron enters into it in any direction.

Solution

Question 7

circular

elliptical

spiral

a straight line

Solution

Question 8

will decrease

will increase

will remain constant

may in crease or decrease

Solution

Question 9

there will be no effect on its motion

the electron will travel along a circle and its speed remains unchanged

the electron will follow the path of a parabola and its speed will increase

the velocity will increase in magnitude but its direction will remain unchanged.

Solution

Question 10

particle velocity

particle acceleration

linear momentum of the particle

kinetic energy of the particle

Solution

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$K_1 > K_2 > K$

$K_1 = K_2 > K$

$K_1 = K_2 = K$

$K_1 < K_2 < K$

$\alpha$ partcle

protons path will be less curved than electrons

path