Moving Charges and Magnetism Test

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Moving Charges and Magnetism Test - 24

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Weekly Quiz Competition

Question 1
1 / -0

A charge q is moving with a velocity v parallel to a magnetic field B. Force on the charge due to magnetic field is

A
qvB

B
qB/v

C
Zero

D
Bv/q

Solution

$$ F + q(\vec{V}\times \vec{B})$$
$$\overrightarrow{V}||\overrightarrow{B},\theta=0$$
$$F=0$$
Question 2
1 / -0

The following cases in which no force is exerted by a magnetic field on a charge is

A
moving with constant velocity

B
moving in a circle

C
at rest

D
moving along a curved path

Solution

$$F_B=q(\overrightarrow{v}\times \overrightarrow{B})$$
if $$v=0, F_B=0$$
Question 3
1 / -0

Two streams of electrons are moving parallel to each other in the same direction. They_____

A
attract each other

B
repel each other

C
cancel the electric field of each other

D
cancel the magnetic field of each other

Solution

If the beams were stationary, they'd repel (because negative charges repel). Once the beams are moving we get the magnetic effects in addition, which reduces the repulsion. The magnetic attraction only becomes strong enough to cancel the electric repulsion at c. Therefore the streams will repel each other due to electric repulsion.
Question 4
1 / -0

The coil of the moving coil galvanometer is wound over an aluminium frame

A
because aluminium is a good conductor

B
because aluminium is very light.

C
because aluminium is comparatively cheaper

D
to provide electro-magnetic damping.

Solution

The coil of the moving galvanometer is wound over an aluminium frame to provide electro-magnetic damping because aluminium is diamagnetic and it does not interact with external magnetic field.
Question 5
1 / -0

The restoring couple in the moving coil galvanometer is due to

A
current in the coil

B
magnetic field of the magnet.

C
material of the coil.

D
twist produced in the suspension wire.

Solution

When coil rotates the spring is twisted and it exerts an opposing torque on the coil.
Question 6
1 / -0

Two streams of protons move parallel to each other in the same direction. They will

A
attract each other

B
repel each other

C
neither attract nor repel

D
rotate

Solution

Two streams of protons move parallel to each other in the same direction. So, we can assume that they are two wires carrying current in same direction. We know that two parallel wires having same direction of current attract each other.
Question 7
1 / -0

Imagine that you are seated in a room and there is a uniform magnetic field pointing vertically downwards in it . At the center of the room an electron is projected horizontally with a certain speed. The path of the electron in this field are:

A
electron moves in anticlockwise path

B
electron moves in clockwise path

C
electron moves left wards

D
electron moves right wards

Solution

$$F = q (\vec{V}\times \vec{B})$$
Assuming observe is looking from top.
So, Force will be in left direction by left hand rule.
So, electron moves in left wards and moves in anti-clock-wise direction.
Question 8
1 / -0

In a moving coil galvanometer a radial magnetic field is applied with concave magnetic poles, to have
A) uniform magnetic field
B) the plane of the coil parallel to field
Choose the correct option among the following

A
both A and B are true

B
both A and B false

C
A is true , B is false

D
A is false, B is true

Solution

In moving coil galvanometer a radial magnetic field is applied with concave magnetic poles, to have uniform magnetic field.
Since the magnified field is radial the plane of the coil is parallel to the magnetic field $$\vec{B}$$ such that $$\theta$$ $$=90^o$$ and hence $$\tau=NIBA$$.
The plane of coil is parallel to the field.
Question 9
1 / -0

There will be no force experienced if

A
two parallel wires carry currents in the same direction

B
two parallel wires carry currents in the opposite direction

C
a positive charge is projected between the pole pieces of a bar magnet

D
a positive charge is projected along the axis of a solenoid carrying current

Solution

Two parallel wires carrying currents in same direction attract each other.
Two parallel wires carrying currents in opposite direction repel each other.
A positive charge is projected between the pole pieces of bar magnet feels a force = $$q(\vec{V}\times \vec{B})$$ which is non zero since angle between V and B is non-zero.
A positive charge projected along the axis of a solenoid carrying current feels no force because in solenoid B is along the axis so $$\vec{V}\times \vec{B}$$ is zero.
Question 10
1 / -0

The radial magnetic field is used in a suspended coil galvanometer to provide

A
a uniform torque on the coil

B
maximum torque on the coil in all positions

C
a uniform and maximum torque in all positions

of the coil

D
a non uniform torque on the coil

Solution

Radial magnetic field is used in a suspended coil galvanometer to provide a uniform torque on the coil because it provide uniform magnetic field.
It ensure that the magnetic field is radial and uniform through out the area of the coil

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Moving Charges and Magnetism Test - 24

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Question 1

qvB

qB/v

Zero

Bv/q

Solution

Question 2

moving with constant velocity

moving in a circle

at rest

moving along a curved path

Solution

Question 3

attract each other

repel each other

cancel the electric field of each other

cancel the magnetic field of each other

Solution

Question 4

because aluminium is a good conductor

because aluminium is very light.

because aluminium is comparatively cheaper

to provide electro-magnetic damping.

Solution

Question 5

current in the coil

magnetic field of the magnet.

material of the coil.

twist produced in the suspension wire.

Solution

Question 6

attract each other

repel each other

neither attract nor repel

rotate

Solution

Question 7

electron moves in anticlockwise path

electron moves in clockwise path

electron moves left wards

electron moves right wards

Solution

Question 8

both A and B are true

both A and B false

A is true , B is false

A is false, B is true

Solution

Question 9

two parallel wires carry currents in the same direction

two parallel wires carry currents in the opposite direction

a positive charge is projected between the pole pieces of a bar magnet

a positive charge is projected along the axis of a solenoid carrying current

Solution

Question 10

a uniform torque on the coil

maximum torque on the coil in all positions

a uniform and maximum torque in all positionsof the coil

a non uniform torque on the coil

Solution

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a uniform and maximum torque in all positions

of the coil