Moving Charges and Magnetism Test

Result

Moving Charges and Magnetism Test - 57

Score
-
out of -
Rank
-
out of -

TIME Taken - -

SHARING IS CARING

If our Website helped you a little, then kindly spread our voice using Social Networks. Spread our word to your readers, friends, teachers, students & all those close ones who deserve to know what you know now.

Weekly Quiz Competition

Question 1
1 / -0

A wire of length $$1m$$ is moving at a speed of $$2m{ s }^{ -1 }$$ perpendicular to its length in a homogeneous magnetic field of $$0.5T$$. If the ends of the wire are joined to a circuit of resistance the $$6 \Omega $$, then the rate at which work is being done to keep the wire moving at constant speed is

A
$$1W$$

B
$$\cfrac { 1 }{ 3 } W$$

C
$$\cfrac { 1 }{ 6 } W$$

D
$$\cfrac { 1 }{ 12 } W$$

Solution

Rate of work $$\cfrac { W }{ t } =P$$
But $$P=Fv$$
Also, $$F=Bil=B\left( \cfrac { Bvl }{ R } \right) l$$
[$$\because$$ induced current $$i=\cfrac { Bvl }{ R } $$]
$$\therefore P=B\left( \cfrac { Bvl }{ R } \right) lv=\cfrac { { B }^{ 2 }{ v }^{ 2 }{ l }^{ 2 } }{ R } =\cfrac { { (0.5) }^{ 2 }\times { (2) }^{ 2 }\times { (1) }^{ 2 } }{ 6 } =\cfrac { 1 }{ 6 } W$$
Question 2
1 / -0

The force $$F$$ acting on charge $$q$$ moving with velocity $$v$$ perpendicular to magnetic field $$B$$ is:

A
$$F = qvB$$

B
$$F = \dfrac {qv}{B}$$

C
$$F = \dfrac {qB}{v}$$

D
$$F = \dfrac {Bv}{q}$$

Solution

Magnetic force $$F = q(v\times B) = qvB \ \sin\theta$$
where $$\theta$$ is the angle between $$v$$ and $$B$$.
Given : $$\theta = 90^o$$
Thus, force $$F = qvB\times \sin90^o = qvB$$
Question 3
1 / -0

A particle with certain charge enters a region of constant, uniform and mutually orthogonal fields E and B with a velocity u perpendicular to both E and B and comes out without any change in magnitude or direction u. This means that

A
Force acting on particle is Inclined at an angle of $$180^o$$

B
Force acting on particle is highly directional

C
Force acting on charged particle is zero

D
Charge on particle is too high

Solution

Force acting on changed particle is zero, as v of changed particle remains constant
$$F= q(v\times B) $$
Question 4
1 / -0

Which one of the following is not correct about Lorentz Force?

A
In presence of electric field $$\bar{E} (r)$$ and magnetic field $$\bar{B} (r)$$ the force on a moving electric charge is $$\bar{F} = q[\bar{E}(r) + \vec{v} \times \bar{B}(r)]$$.

B
The force, due to magnetic field on a negative charge is opposite to that on a positive charge.

C
The force due to magnetic field become zero if velocity and magnetic field are parallel or antiparallel.

D
For a static charge the magnetic force is maximum.

Solution

If charge is not moving then the magnetic force is zero.
Since $$\overset{\rightarrow}{F_m} = q( \overset{\rightarrow}{v} \times \overset{\rightarrow}{B})$$
As $$\overset{\rightarrow}{v} =0$$, for stationary charge. $$\therefore \overset{\rightarrow}{F_m} = 0$$
So in this case minimum force will act on the charge partical.
Option D
Question 5
1 / -0

The net magnetic flux through any closed surface, kept in a magnetic field is

A
zero

B
$$\dfrac{\mu_0}{4 \pi}$$

C
$$4 \pi \mu_0$$

D
$$\dfrac{4 \mu_0}{\pi}$$

Solution

The net magnetic flux through any closed surface will be zero, i.e. $$\oint \bar{B} . d \bar{s} = 0$$, because there are no magnetic monopoles.
Question 6
1 / -0

A particle with a specific charge s is fired with a speed v 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?

A
$$\frac{v}{sd}$$

B
$$\frac{2v}{sd}$$

C
$$\frac{v}{2sd}$$

D
$$\frac{v}{4sd}$$

Solution
Question 7
1 / -0

In an inertial frame of reference, the magnetic force on a moving charged particle is $$\bar{F}$$. Its value in another internal frame of reference will be

A
remain same

B
changed due to change in the amount of charge

C
changed due to change in velocity of charged particle

D
changed due to change in field direction

Solution

$$\overset{\rightarrow}{F} = \overset{\rightarrow}q ( \overset{\rightarrow}{v} \times \overset{\rightarrow}{B}) \,\, \,\, \therefore F = qv B sin \theta$$
which shows magnetic force is velocity dependent due to which it differs from one inertial frame to another.
Question 8
1 / -0

$$r=\frac{mv}{qB}$$
Time spent in magnetic field
$$t=\frac{\pi m}{qB}$$

A
First and second statements are true.

B
First and second statements are false.

C
First is true second is false.

D
First is false second is true.

Solution
Question 9
1 / -0

Imagine yourself to be swimming in the wire in the direction of the current and facing a magnetic needle, then the north pole of the needle is deflected towards your left hand. Which is this rule?

A
Ampere's rule

B
Faraday right hand rule

C
Faraday left hand rule

D
Maxwell's rule

Solution
Question 10
1 / -0

Two free parallel wires carrying currents in opposite directions.

A
Do not affect each other

B
Attract each other

C
Repel each other

D
None of these

Solution