Physics

Magnetism and Electromagnetism

1,011 Questions

This hub provides practice questions on magnetism and electromagnetism. It covers magnetic flux density, electromagnets, magnetic lines of force, and electromagnetic induction. These physics concepts frequently appear in technical and non-technical competitive exams.

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Magnetism and Electromagnetism Questions

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

All magnetic materials lose their magnetic properties when :

  1. Dipped in water

  2. Dipped in oil

  3. Brought near a piece of iron

  4. Strongly heated
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
All the magnetic material lose their magnetic properties when strongly heated.
Every magnetic materials have a temperature called the curle point; above which they will lose their magnetism.
OPTION : D.
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 fun with magnets let's make a magnet making magnets making and handling magnets

Soft iron pieces are placed across the ends of bar magnets when stored. Such pieces are called :

  1. preservatives

  2. keepers

  3. compasses

  4. poles
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Soft iron pieces are placed across the ends of bar magnets when stored; such pieces are called magnetic keepers. If the two magnets are placed side by side there will be mutual repulsion or attraction that weakens the magnetic strength. So magnets are placed side by side with opposite poles near to each other.

Multiple choice physics current electricity and magnetism electric bell the magnetic effect of a current electromagnetic forces oersted experiment oersted's experiment magnetic field due to a straight current carrying conductor

Working of electric bells is an example of

  1. Mechanical effect of electric current

  2. Heating effect of electric current

  3. Magnetic effect of electric current

  4. None of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

An electric bell contains an electromagnet, consisting of coils of insulated wire wound round iron rods. When an electric current flows through the coils, the rods become magnetic and attract a piece of iron attached to a clapper. The clapper hits the bell and makes it ring.

Multiple choice physics current electricity and magnetism electric bell the magnetic effect of a current electromagnetic forces oersted experiment oersted's experiment magnetic field due to a straight current carrying conductor

Which of the following is not a component of electric bell?

  1. Gong

  2. Ferromagnetic strip

  3. Low magnetic field permanent magnet to attract ferromagnetic strip

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

Electric bell works on the mechanism of electromagnets i.e, temporary magnets, and no permanent magnet is used.

Temporary magnet allows the ferromagnetic strip to return back to its initial state as switch is released.

Multiple choice physics current electricity and magnetism electric bell the magnetic effect of a current electromagnetic forces oersted experiment oersted's experiment magnetic field due to a straight current carrying conductor

What will happen if the strip in a doorbell loses its flexibility?

  1. Striker may break if current is large.

  2. After hitting the metal gong, it never returns to original position and only a single sound is produced.

  3. System of doorbell breaks

  4. Both A and B
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Because of lack of flexibility, striker will resist change of motion more and may break if current is large.

Without flexibility, no rebounding force is present and striker will not return to its original position.

Multiple choice physics current electricity and magnetism electric bell the magnetic effect of a current electromagnetic forces oersted experiment oersted's experiment magnetic field due to a straight current carrying conductor

During a doorbell ringing

  1. Current always flows in the circuit

  2. Electromagnet is always present

  3. Striker is always in contact with metal gong

  4. Striker always repeatedly hits metal gong
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Striker repeatedly hits the metal gong when doorbell is ringing. 

This can be observed in regular bells used at homes.

Multiple choice physics current electricity and magnetism electric bell the magnetic effect of a current electromagnetic forces oersted experiment oersted's experiment magnetic field due to a straight current carrying conductor

Armature is pulled towards the spring when it strikes the gong because

  1. The electromagnet gets demagnetized

  2. The current flow breaks

  3. Spring effect

  4. All of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The working of an electric magnet is based on the magnetic effect of current. When the key is pressed the circuit gets completed and current passes through it causing the electromagnet to get magnetized which in turn attracts the armature. This movement of the armature causes the hammer to strike the gong. However when the armature moves towards the gong the connection between the spring strip and adjusting screw is lost which breaks the circuit and the current flow is stopped thus demagnetizing the electromagnet. This causes the armature to return to its original position and it is thus pulled back due to the spring effect of the spring strip. This process is called a make and break circuit.

Multiple choice physics current electricity and magnetism electric bell the magnetic effect of a current electromagnetic forces oersted experiment oersted's experiment magnetic field due to a straight current carrying conductor

Which process is applied on a circuit for the working of an electric bell?

  1. Magnetization

  2. Make and break

  3. Both A and B

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

The working of an electric magnet is based on the magnetic effect of current. When the key is pressed the circuit gets completed and current passes through it causing the electromagnet to get magnetized which in turn attracts the armature. This movement of the armature causes the hammer to strike the gong. However when the armature moves towards the gong the connection between the spring strip and adjusting screw is lost which breaks the circuit and the current flow is stopped thus demagnetizing the electromagnet. This causes the armature to return to its original position and it is thus pulled back due to the spring effect of the spring strip. This process is called a make and break circuit.

Multiple choice physics current electricity and magnetism electric bell the magnetic effect of a current electromagnetic forces oersted experiment oersted's experiment magnetic field due to a straight current carrying conductor

The hammer hits the gong because

  1. It has electric charge

  2. It displays the spring effect

  3. It is attracted towards the electro-magnet

  4. All of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The working of an electric magnet is based on the magnetic effect of current. When the key is pressed the circuit gets completed and current passes through it causing the electromagnet to get magnetized which in turn attracts the armature. This movement of the armature causes the hammer to strike the gong.

Multiple choice properties of magnet magnetic field moving charges and magnetism magnetic effects of current and magnetism physics

Pick correct statements from among the following : 
a) Electric field and magnetic field are basically independent
b) Electric field and magnetic field are to aspects of the electromagnetic field
c) Electric field and magnetic field may be produced by charge at rest
d) A moving charge produces both electric and magnetic fields

  1. a and b are correct

  2. b and d are correct

  3. b, c and d are correct

  4. a, c and d are correct
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Electric field and magnetic field are not independent. They are two aspects of the electromagnetic field. Charge at rest only produces electric field. Moving charge produces both electric field and magnetic field.