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.

Q: An electric bell has a resistance of \$5 \Omega\$ and requires a current of \$0.25\ A\$ to work it. Assuming that the resistance of the bell wire is \$1 \Omega\$ per \$15m\$ and that the bell push is \$90m\$ distance from the bell. How many cells each of emf \$1.4V\$ and internal resistance \$2 \Omega\$, will be required to work the circuit.

\$\textbf{Given}:\$ \$i=0.25A, E=1.4V\$ \$\textbf{Solution}:\$Total resistance of the wire=\$5\Omega\$Now, Resistance per unit length\$\rho = \dfrac{1}{15}\$ \$\Omega/m\$Also\$R_W = \dfrac{1}{15}\times90\$ = \$6\Omega\$And, let there be n cells\$R_{eq} = [6+5+n(2)]\$There are n cells, so\$i= 0.25\$ \$=\frac{V_{eq}}{R_{eq}}=\$\$\dfrac{nE}{R_{eq}}\$\$\dfrac{1}{4}=\dfrac{n\times 1.4}{11+2n}\$\$\therefore n = 3.05\approx 3\$\$\textbf{Hence C is the correct option}\$

Question 1

Explain the construction and working of electric bell with figure.

Accepted Answer

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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

$\text{Working}$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.

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

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 6

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

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 7

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 8

Why is soft iron used as the core of the electromagnet in an electric bell?

Accepted Answer

An electric bell consists of one or more electromagnets, made of a coil of insulated wire around an iron bar, which attract an iron strip armature with a clapper.The soft iron bar acquires the magnetic properties only when an electric current flows through the coil and loses the magnetic properties as the current is switched off. That's why soft iron is used as the core of the electromagnet in an electric bell.Because it serves the purpose of a temporary magnet that can be turned off or on accordingly.

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

An electric bell has a resistance of $5 \Omega$ and requires a current of $0.25\ A$ to work it. Assuming that the resistance of the bell wire is $1 \Omega$ per $15m$ and that the bell push is $90m$ distance from the bell. How many cells each of emf $1.4V$ and internal resistance $2 \Omega$, will be required to work the circuit.

Accepted Answer

$\textbf{Given}:$ $i=0.25A, E=1.4V$ $\textbf{Solution}:$Total resistance of the wire=$5\Omega$Now, Resistance per unit length$\rho = \dfrac{1}{15}$ $\Omega/m$Also$R_W = \dfrac{1}{15}\times90$ = $6\Omega$And, let there be n cells$R_{eq} = [6+5+n(2)]$There are n cells, so$i= 0.25$  $=\frac{V_{eq}}{R_{eq}}=$$\dfrac{nE}{R_{eq}}$$\dfrac{1}{4}=\dfrac{n\times 1.4}{11+2n}$$\therefore n = 3.05\approx   3$$\textbf{Hence C is the correct option}$

Working of electric bell

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REVISE WITH CONCEPTS

How Electric Bell Works?

QUICK SUMMARY WITH STORIES

Electric Bell

Construction And Working Of An Electric Bell

Explain the construction and working of electric bell with figure.

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?

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

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

An electric bell has an electromagnet.

The hammer hits the gong in an electric bell because

Why is soft iron used as the core of the electromagnet in an electric bell?

The purpose of armature in an electric bell is

Working of electric bell

Rate

REVISE WITH CONCEPTS

How Electric Bell Works?

QUICK SUMMARY WITH STORIES

Electric Bell

Construction And Working Of An Electric Bell

Explain the construction and working of electric bell with figure.

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?

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

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

An electric bell has an electromagnet.

The hammer hits the gong in an electric bell because

Why is soft iron used as the core of the electromagnet in an electric bell?

The purpose of armature in an electric bell is

An electric bell has a resistance of 5Ω and requires a current of 0.25 A to work it. Assuming that the resistance of the bell wire is 1Ω per 15m and that the bell push is 90m distance from the bell. How many cells each of emf 1.4V and internal resistance 2Ω, will be required to work the circuit.