Question 1

Explain the construction and working of electric bell with figure.

Accepted Answer

The electric bell works on the principle of the electromagnet. Its construction is shown in the above figure.Construction: It is made of an electromagnet, bell(metallic cup), soft iron strip(which works as a hammer) and contact screw. The bell is a cup-shaped device made of metal. A soft iron strip works as a small hammer.Working: When current is passed through the circuit, the electromagnet acts like a magnet and attracts the iron strip. The iron strip(hammer), being elastic, strikes the bell. Simultaneously, its contact with the screw is broken, the circuit breaks and the current stops flowing through the electromagnet. As such, the iron strip returns to its original position, and again the current passes through the electromagnet.This phenomenon happens many times in a second, and as the hammer strikes the bell, the sound is heard. The bell rings till the circuit has been switched off. The electric bell is used in alarms and bells is schools, offices, homes and industries.

Question 2

In the circuit shown in figure, when the circuit is completed, the hammer strikes the gong. Which of the following force is responsible for the movement of hammer?

Accepted Answer

When the electric circuit is completed the electromagnet is activated and the soft iron armature is strongly pulled. The hammer strikes the gong producing the sound.So, the magnetic force  is responsible for the movement of hammer.

Question 3

Draw a neat and labelled diagram of an electric bell and describe its working.

Accepted Answer

ext{Working} When a push button fitted in a battery is pressed, the current flows through the contact points via an electromagnet.The U shaped electromagnet is magnetized and it attracts the armature towards it.The hammer fitted with strip gives a strike on the gong producing sound.The moment this happens, contact of the attached spring with screw is broken, i.e. the circuit is broken.As a result, current stops flowing and the electromagnet is demagnetized.Due to this action of the spring, armature comes to its previous position, i.e. comes in contact with the screw and the circuit is again completed.Each approach of the armature or strip causes the hammer to strike the gong.Thus, the same process is repeated many times and the bell goes on ringing.

Question 4

How does the magnetic effect of electric current help in the working of an electric bell? Explain with the help of a diagram.

Accepted Answer

The circuit of electric circuit is given below:When we switch ON the circuit, electric current flows through the coil. According to the magnetic effect of current, the coil gets magnetized. This magnetized coil attracts nearby soft iron armature. Also because of this, the hammer strikes the gong (bell) to generate a sound. So, the bell starts buzzing. When we switch OFF the circuit, the magnetization of the coil and flow of current will stop. So, the bell stops buzzing.

Question 5

Read the extract given below and answer the question that follows:

The trees inside are moving out into the forest,
the forest that was empty all these days
where no bird could sit
no insect hide
no sun bury its feet in shadow
the forest that was empty all these nights
will be full of trees by morning.

The figure of speech used in these lines is _________ .
(i) Simile
(ii) Alliteration
(iii) Personification
(iv) Metonymy

Q: Draw a neat and labelled diagram of an electric bell and describe its working.

\text{Working} When a push button fitted in a battery is pressed, the current flows through the contact points via an electromagnet.The U shaped electromagnet is magnetized and it attracts the armature towards it.The hammer fitted with strip gives a strike on the gong producing sound.The moment this happens, contact of the attached spring with screw is broken, i.e. the circuit is broken.As a result, current stops flowing and the electromagnet is demagnetized.Due to this action of the spring, armature comes to its previous position, i.e. comes in contact with the screw and the circuit is again completed.Each approach of the armature or strip causes the hammer to strike the gong.Thus, the same process is repeated many times and the bell goes on ringing.

Accepted Answer

When the push switch is depressed, the circuit is closed. Current passes through the electromagnet winding and the core becomes magnetized. The magnetized core attracts the iron armature which makes the striker hits the gong. However, the movement of the armature opens the make and break switch which switches the electromagnet off. The iron armature springs back to its original position, closing the make and break switch and start the cycle again. Soft iron core is used to make electromagnets as it gains and losses magnetism quickly depending on existence of magnetic fields. The armature is also made of soft iron which can induce magnetism rapidly. No matter what direction is the current flow, the bell rings continuously as long as the push switch is closed because any pole induces the armature.

Question 6

The hammer hits the gong in an electric bell because

Accepted Answer

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.

Question 7

An electric bell has an electromagnet.

Accepted Answer

An electric bell works with the help of an electromagnet. It is made up of a coil of wire wound on an iron piece, which acts as an electromagnet. On passing the current, the magnetic field is produced by the electromagnet. The hammer of the bell is attracted towards the electromagnet when the circuit is complete.

Question 8

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

Accepted Answer

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.

Question 9

The purpose of armature in an electric bell is

Accepted Answer

The purpose of armature in an electric bell is 1. to make and break the circuit 2. to produce sound.

Question 10

The material used for making the armature of electric bell is

Accepted Answer

An electric bell contains an electromagnet, consisting of coils of insulated wire wound round iron rods.When the push switch is depressed, the circuit is closed. Current passes through the electromagnet winding and the core becomes magnetized. The magnetized core attracts the iron armature which makes the striker hits the gong. However, the movement of the armature opens the make and break switch which switches the electromagnet off. The iron armature springs back to its original position, closing the make and break switch and start the cycle again. Soft iron is used to make electromagnets as it gains and losses magnetism quickly depending on existence of magnetic fields. The armature is also made of soft iron which can induce magnetism rapidly. No matter what direction is the current flow, the bell rings continuously as long as the push switch is closed because any pole induces the armature.

Working of electric bell

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