Tag: electro-magnetism

Quizzes (12) Questions (113)

Questions Related to electro-magnetism

Multiple choice physics electro-magnetism applications of electromagnets

A permanent magnet in the shape of a thin cylinder of length $10$cm has magnetisation (M) $=10^6$A $m^{-1}$. It's magnetization current $I _M$ is?

  1. $10^5$A

  2. $10^6$A

  3. $10^7$A

  4. $10^8$A
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Given:

 The length of the thin cylinder is $10\ cm$.
The magnetization of the magnet is $10^6 A/m$

The magnetization current is given by:
$I _M=M\times l$

$I _M=10^6\times 0.1$

$\Rightarrow10^5\ A$

Multiple choice physics electro-magnetism applications of electromagnets

The strength of an electromagnet can be increased by. 

  1. increasing the current in the coil

  2. decreasing the current in the coil

  3. decreasing the number of turns in the coil

  4. increasing the length of air gap between its poles
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Answer is A.

The strength of an electromagnet can be increased by increasing the number of loops of wire around the iron core and by increasing the current or voltage.

Multiple choice physics electro-magnetism applications of electromagnets

For making a strong electromagnet, the material of the core should be

  1. soft iron

  2. steel

  3. brass

  4. copper
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Soft iron is used for making strong electromagnet.

Electromagnets are temporary magnets.

Multiple choice physics electro-magnetism applications of electromagnets

strength of electromagnet increases when

  1. <span>the number of turns in the coil increases</span>

  2. <span>the current flowing in the coil increases</span>

  3. both a and b

  4. <span>the number of turns in the coil decreases</span>
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
we know that
$\vec B=\dfrac{\mu NI}{L}$ where,
$\vec B$= Magnetic strength
N= number of turns
I= Current
L= Length of coil gap, and
$\vec B=\text{ magnetic field }\propto N$
$\vec B \propto I$
$\vec B\propto 1/2$
Thus
$B\left( \uparrow  \right) \text{ with } N\left( \uparrow  \right) \text{ and }I\left( \uparrow  \right) $

Multiple choice physics electro-magnetism applications of electromagnets

Two electromagnets are made by wrapping a few turns of wire on similar nails and passing the same amount of electric current through them.The number of turn of the wire wrapped over the two iron nails are in the ratio 2:1.The strength of   

  1. The first electromagnet will be greater

  2. The second electromagnet will be greater

  3. Both the electromagnets will be equal

  4. Electromagnets has no relation with the number of turns
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

More the number of coils, more will be the magnetic field produced in the electromagnets and hence made the electromagnet stronger. As number of turns wrapped on the first iron nail is more, thus the first electromagnet has more strength.

Multiple choice physics electro-magnetism applications of electromagnets

An example of a perfect diamagnet is a superconductor . This implies that when a superconductor is put in a magnetic field of intensity $B$, the magnetic field ${B _s}$ inside the superconductor will be such that:

  1. ${B _s} = - B$

  2. ${B _s} = 0$

  3. ${B _s} = B$

  4. ${B _s} &lt; B but\,{B _s} \ne 0$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A perfect diamagnet (superconductor) exhibits the Meissner effect, where it expels all magnetic flux from its interior, resulting in a magnetic field of zero inside.

Multiple choice physics electro-magnetism applications of electromagnets

One bar magnet and one coil both are in a steady state. North pole of the magnet is towards the coil, then this end of the coil becomes. 

  1. north pole

  2. south pole

  3. have no magnetic pole

  4. north and south pole any of that
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

If the magnet and coil are in a steady state (no relative motion), there is no change in magnetic flux through the coil. Therefore, no induced current is produced, and the coil does not act as a magnet.

Multiple choice physics electro-magnetism applications of electromagnets

The phenomeno of paramagnetism is a consequnce of 

  1. Distortion effect.

  2. Orientation effect

  3. Both (A) and (B)

  4. Neither (A) nor (B)
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Paramagnetism arises from the tendency of atomic magnetic moments to align with an external field (orientation effect) and the competition against thermal agitation (distortion effect).

Multiple choice physics electro-magnetism applications of electromagnets

Complete the given statement, the strength of an electromagnet can be:

  1. increased by adding a ferromagnetic core

  2. decreased by adding turns of wire to the coil

  3. increased by reducing the current through the wire

  4. increased by adding an aluminum core

  5. decreased by adding more layers of wire to the coil
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A ferromagnetic substance get highly magnetized when put in a magnetic field. When the ferromagnetic core is added to the electromagnet then the total field is the sum of the field because of electromagnet and because of the highly magnetized core.

Multiple choice ac and dc ac vs dc electro-magnetism effects of electric current physics

The advantage of ac over dc is that:

  1. its generation cost is much less.

  2. it contains more electric energy.

  3. it is free from voltage fluctuations.

  4. it can be transmitted over long distances with minimum power loss.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Answer is B.

The advantage of AC over DC is that power transmission is simpler under AC, it can be changed in voltage relatively easily using transformers, and that higher power motors can be devised under AC. It contains more electric energy.