Tag: properties of a magnetic field

Questions Related to properties of a magnetic field

Magnets lose their properties if :

physics properties of a magnetic field let's make a magnet making magnets making and handling magnets

  1. A.C. is passed through them

  2. heated strongly

  3. dropped from a height

  4. all of the above

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Correct Option: A,B
Explanation:

When a magnet is treated above 176℉ (80)℃ magnet will quickly loose their magnetic properties. The magnet will become permanently demagnetized if exposed to those temperatures for a certain length of time.

By passing an alternating current the magnetic property can be removed because the alternating current produces a reverse magnetizing field which opposes the object magnetism.

 

A.  Ferromagnetic materials will lose their magnetism if heated above a point known as the Curie temperature.
B. You would have to re-magnetize the magnet again, either in a solenoid or with another permanent magnet, in order to restore the magnetism.
C. If you heat a magnet up a little bit, it will lose some of its magnetism, but on returning to room temperature full magnetism can be restored. 
Which among the following is/are true?

physics properties of a magnetic field let's make a magnet making magnets making and handling magnets

  1. Only A

  2. Both A and B

  3. Only C

  4. All A, B and C

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Correct Option: D
Explanation:

All the three statements are true that the ferromagnetic materials lose their magnetism on heating above the Curie temperature,

The magnet has to re-magnetized with another magnet or solenoid to restore its magnetism and the magnetism of the magnet is fully recovered when it is kept at room temperature after heating.

By which of the following activity, a magnet can loose its property?

physics properties of a magnetic field let's make a magnet making magnets making and handling magnets

  1. Excess of heating

  2. Demagnetizing magnetic field

  3. Sudden shock

  4. All of the above

Show answer
Correct Option: D
Explanation:
A magnet shows magnetic behavior because of the presence of domains which are specific formations consisting of electrons which exhibit magnetic behavior.
By all these actions, all the arranged magnetic domains which exhibit magnetic property due to their specific arrangement get rearranged and that specific formation of magnetic domain which is responsible for its magnetic behavior is destroyed.
And hence the magnet will loose its magnetic behavior.

A mixture of iron and nickel can be easily magnetized, even in a weak field. Which results in the formation of a ________. Fill in the blank.

physics properties of a magnetic field let's make a magnet making magnets making and handling magnets

  1. Permanent Magnet

  2. Electromagnet

  3. Temporary Magnet

  4. None of the above

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Correct Option: C
Explanation:

A mixture of iron and nickel is magnetized by applying an external magnetic field. This convert the mixture into a temporary magnet for the time when the field has been applied.

A magnet can induce magnetism in

physics properties of a magnetic field let's make a magnet making magnets making and handling magnets

  1. brass

  2. aluminium

  3. glass

  4. steel

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Correct Option: A
Explanation:

As the magnet can include the magnetism is femo magnetic materials.

Only, Brass is a I.M material.

State whether true or false :
Magnetization by electric current method creates more powerful magnets than other  methods of magnetization.

physics properties of a magnetic field let's make a magnet making magnets making and handling magnets

  1. True

  2. False

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Correct Option: A
Explanation:

Magnetization. There are a variety of methods that can be used to establish a magnetic field in a component for evaluation using magnetic particle inspection. It is common to classify the magnetizing methods as either direct or indirect. With direct magnetization, current is passed directly through the component.Rubbing the nail with the permanent magnet causes a stronger, more lasting magnetism in the nail. For this to work, only one pole of the magnet must stroke the nail from one end to the other in a single direction. ... It usually takes around 20 to 30 strokes before the nail becomes sufficiently magnetized.

For a permanent magnet, properties of material should be

physics properties of a magnetic field let's make a magnet making magnets making and handling magnets

  1. high retentivity high coercivity

  2. low retentivity law coercivity

  3. high retentivity low coercivity

  4. low retentivity high coercivity

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Correct Option: A

A rod of cross-sectional area $10$ $cm^2$ is placed with its length parallel to a magnetic field of intensity $1000$ ${A/m}$ , the flux through the rod is $10^4$ $webers$. Then the permeability of material of the rod is:

physics properties of a magnetic field let's make a magnet making magnets making and handling magnets

  1. $10^4$ ${wb/Am}$

  2. $10^3$ ${wb/Am}$

  3. $10^2$ ${wb/Am}$

  4. $10$ ${wb/Am}$

Show answer
Correct Option: A
Explanation:
Magnetic field of intensity $(H)=1000\ A/m$
$Flux$ through rod $(\phi)=10^4 \ Wb$
Area of mass section $(A)=10\ cm^2 =10\times 10^{-4}m^2$
$\Rightarrow \ A=10^{-3}m^2$

we know,
$\boxed {B=\dfrac {\phi}{A}= \mu H}$           (where $B$ is magnetic flux density)
  $\Rightarrow \ \dfrac {10^4}{10^{-3}}= \mu (1000)$
$\ \Rightarrow \ \mu =\dfrac {10^4}{10^{-3} \times 1000}=10^4\ Wb /Am$

hence $\boxed {\mu =10^4 \ Wb/Am}$,

so $(A)$ option is correct

permeability of material of rod

A domain in a ferromagnetic substance is in form of a cube of side length $1 \,\mu m$. It is contains $8 \times 10^{10}$ atoms and each atomic dipole has a moment of $9 \times 10^{-24} A \,m^2$, then the magnetization of the domain is then

physics properties of a magnetic field let's make a magnet making magnets making and handling magnets

  1. $7.2 \times 10^5 \,A \,m^{-1}$

  2. $7.2 \times 10^3 \,A \,m^{-1}$

  3. $7.2 \times 10^9 \,A \,m^{-1}$

  4. $7.2 \times 10^{12} \,A \,m^{-1}$

Show answer
Correct Option: A
Explanation:

Magnitisation $= \dfrac{M}{v}$

$= \dfrac{8 \times 10^{10} \times 9 \times 10^{-24}}{(10 - 6)^3}$

$= 7.2 \times 10^5 \,Am^{-1}$

The magnetic force required to demagnetize the material is called:

physics properties of a magnetic field let's make a magnet making magnets making and handling magnets

  1. Retentivity

  2. Coercivity

  3. Energy loss

  4. Hysteresis

Show answer
Correct Option: B
Explanation:

The coercivity of a substance is a measure of the reverse magnetising field required to destroy the residual magnetism of the substance.