Tag: properties of a magnetic field

Quizzes (4) Questions (45)

Questions Related to properties of a magnetic field

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

Magnets lose their properties if :

  1. A.C. is passed through them

  2. heated strongly

  3. dropped from a height

  4. all of the above
Reveal answer Fill a bubble to check yourself
A,B Correct answer
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.

 

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

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?

  1. Only A

  2. Both A and B

  3. Only C

  4. All A, B and C
Reveal answer Fill a bubble to check yourself
D Correct answer
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.

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

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

  1. Excess of heating

  2. Demagnetizing magnetic field

  3. Sudden shock

  4. All of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
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.
Multiple choice physics properties of a magnetic field let's make a magnet making magnets making and handling magnets

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.

  1. Permanent Magnet

  2. Electromagnet

  3. Temporary Magnet

  4. None of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
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.

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

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

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

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

For a permanent magnet, properties of material should be

  1. high retentivity high coercivity

  2. low retentivity law coercivity

  3. high retentivity low coercivity

  4. low retentivity high coercivity
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A permanent magnet needs to retain its magnetism (high retentivity) and resist demagnetization by external fields (high coercivity).

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

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:

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

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

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

  4. $10$ ${wb/Am}$
Reveal answer Fill a bubble to check yourself
A Correct answer
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
Multiple choice physics properties of a magnetic field let's make a magnet making magnets making and handling magnets

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

  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. $7.2 \times 10^{12} \,A \,m^{-1}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

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

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

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