Magnetism and Matter Test -9

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Magnetism and Matter Test -9

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Weekly Quiz Competition

Question 1
1 / -0

What is the unit of magnetic flux?

A
Dynes

B
Oerested

C
Gauss

D
Weber

Solution
Question 2
1 / -0

According to Curie's law, the magnetic susceptibility of a substance at an absolute temperature T is proportional to -

A
$$1/T$$

B
$$T$$

C
$$1/T$$$$^{2}$$

D
$$T$$$$^{2}$$

Solution

Curie law $$\chi _{m}\infty \frac{1}{T}$$
Question 3
1 / -0

A paramagnet magnet behaves like a solenoid because both contain currents in the form of

A
Circles

B
Parabola

C
Straight line

D
Ellipse

Solution

A paramagnet magnet behaves like a solenoid because both contain currents in the form of circle. The magnetic field is generated by the circular motion of the electron inside the atom.
Question 4
1 / -0

An electron moves with a constant speed v along a circle of radius r. The magnetic moment will be (e is the electron charge).

A
evr

B
$$\dfrac{1}{2}evr$$

C
$$\pi r^{2}ev$$

D
$$2\pi rev$$

Solution

magnetic moment
$$= niA$$
$$= (1)\dfrac{e}{t}\pi r^2$$
$$= \dfrac{ew}{2\pi}\pi r^2$$ $$(\because t = \dfrac{2\pi}{w})$$
$$= \dfrac{evr}{2}$$ $$(\because v = wr)$$
Question 5
1 / -0

Two conducting circular loops F and G are kept in a plane on either side of a straight current-carrying wire as shown in the figure below.
If the current in the wire decreases in magnitude, the induced current in the loops will be

A
clockwise in F and clockwise in G.

B
anti-clockwise in F and clockwise in G.

C
clockwise in F and anti-clockwise in G.

D
anti-clockwise in F and anti-clockwise in G.

Solution

The magnetic field above the wire is out of the plane. This flux is decreasing and should be compensated by the current in the loop F and so the current in loop F will be anti-clockwise. For loop G the situation is opposite
Question 6
1 / -0

If the angular momentum of an electron of charge $$e$$, revolving in a circular orbit is $$L$$, then its magnetic moment is (Given mass of electron $$=m$$)

A
$$eLm$$

B
$$\dfrac{eL}{m}$$

C
$$\dfrac{eL}{2m}$$

D
$$0$$

Solution

angular momentum
$$L = mVr \Rightarrow \dfrac{L}{m} = Vr =\omega r^2$$
magnetic moment $$= i A$$
$$= \dfrac{e}{T}\pi r^2$$

$$= \dfrac{e\omega}{2\pi}\pi r^2$$ $$(\because T = \dfrac{2\pi}{\omega})$$

$$= \dfrac{e\omega r^2}{2}$$

$$= \dfrac{e}{2}\times \dfrac{L}{m}$$

$$= \dfrac{eL}{2m}$$
Question 7
1 / -0

Magnetic field lines :

A
starts from north pole

B
starts from south pole

C
starts from current-carrying wires

D
are closed loops

Solution
Question 8
1 / -0

The force with which a magnet attracts objects like iron is called ....................... .

A
Electric Force

B
Magnetic Force

C
Electromagnetic faoce

D
gravitational force

Solution

The force which attracts objects like iron is called magnetic force.
The force of attraction or repulsion which are present between two magnetic materials is known as magnetic force iron is a ferromagnetic materials.
Hence, option : B.
Question 9
1 / -0

The magnetising field required to be applied in opposite direction to reduce residual magnetism to zero is called

A
coercivity

B
retentivity

C
hysteresis

D
none of these

Solution

The coercivity is the intensity of the applied magnetic field required to reduce the magnetization of that material to zero.
Question 10
1 / -0

The magnetic moment of an electron with orbital angular momentum $$J$$ will be :

A
$$\dfrac {e\vec J}{m}$$

B
$$\dfrac {e\vec J}{2m}$$

C
$$\dfrac {2m}{e\vec J}$$

D
$$zero$$

Solution

Angular momentum $$J= m\omega r^2$$ where $$\omega$$ is the angular velocity$$, r$$ is the radius of the orbit

Magnetic moment $$\mu = iA=\dfrac{e\omega}{2\pi}\pi r^2$$
$$ \therefore \dfrac{\mu}{J} = \dfrac{\dfrac{e\omega}{2\pi}\pi r^2}{m\omega r^2}=\dfrac{e}{2m}$$
$$ \Rightarrow \vec{ \mu }= \dfrac{e}{2m}\vec{J}$$

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Re-Attempt Weekly Quiz Competition

Magnetism and Matter Test -9

Result

Magnetism and Matter Test -9

Score

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SHARING IS CARING

Question 1

Dynes

Oerested

Gauss

Weber

Solution

Question 2

$$1/T$$

$$T$$

$$1/T$$$$^{2}$$

$$T$$$$^{2}$$

Solution

Question 3

Circles

Parabola

Straight line

Ellipse

Solution

Question 4

evr

$$\dfrac{1}{2}evr$$

$$\pi r^{2}ev$$

$$2\pi rev$$

Solution

Question 5

clockwise in F and clockwise in G.

anti-clockwise in F and clockwise in G.

clockwise in F and anti-clockwise in G.

anti-clockwise in F and anti-clockwise in G.

Solution

Question 6

$$eLm$$

$$\dfrac{eL}{m}$$

$$\dfrac{eL}{2m}$$

$$0$$

Solution

Question 7

starts from north pole

starts from south pole

starts from current-carrying wires

are closed loops

Solution

Question 8

Electric Force

Magnetic Force

Electromagnetic faoce

gravitational force

Solution

Question 9

coercivity

retentivity

hysteresis

none of these

Solution

Question 10

$$\dfrac {e\vec J}{m}$$

$$\dfrac {e\vec J}{2m}$$

$$\dfrac {2m}{e\vec J}$$

$$zero$$

Solution

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