Question 1

State true or false.MCB is a safety device which cuts off the electricity supply  automatically without turning off a switch.

Accepted Answer

MCB stands for miniature circuit breaker. A MCB is an electrical device that is automatically controlled to protect an electrical circuit from damage caused by excess current from overload or short circuiting. MCB prevents damage by automatically breaking the circuit without turning off any switch.

Question 2

Which of the following is the correct method of setting a circuit?

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Question 3

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 4

Name one device that uses an electromagnet.

Accepted Answer

An electromagnet is a type of magnet in which the magnetic field is produced by an electric current. The magnetic field disappears when the current is turned off. Electromagnets usually consist of a large number of closely spaced turns of wire that create the magnetic field. The wire turns are often wound around a magnetic core made of generally iron.  Electromagnets are widely used as components of electrical devices such as Electric Bell ,motors, generators, loudspeakers, hard disks, MRI machines, scientific instruments, etc. Hence option A.

Question 5

An electromagnet is a temporary magnet.

Accepted Answer

An electromagnet is a type of magnet in which the magnetic field is produced by an electric current. Electromagnets usually consist of wire wound into a coil around an iron core.A current through the wire creates a magnetism inside the iron core.And it is a temporary magnet because when current is turned off the magnetism disappears.Then it is no longer a magnet.

Question 6

An electric bell works on the .......... effect of a current and uses an ..........

Accepted Answer

An electric bell works with the principle of working of electromagnetism. When the switch is pushed on, the circuit gets completed and the current starts flowing through the U-shaped electromagnet which creates a magnetic field in the core. This attracts the iron armature. When the armature moves towards the electromagnet, the hammer strikes the gong and the bell rings.

Question 7

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 8

Which one of the following heater element is used in electric press

Accepted Answer

Heating appliances generally contain coils of high resistance wire made of nichrome alloy. When these appliances are connected to power supply by insulated copper wires then a large amount of heat is produced in the heating coils because they have high resistance.

Question 9

A fuse is used in an electrical appliance :

Accepted Answer

Fuse is a device used to prevent overheating of appliances due to a sudden increase in the current in the circuit.It protects the device and the user. When the electric current is higher than the normal current needed by a circuit, the fuse blows up and breaks the circuit.Hence, it protects the circuit from a power overload.

Question 10

An electric bell uses ......... shaped electromagnet for its working.

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Electric Current And Its Effects

Physics
1888 Views

State true or false.
MCB is a safety device which cuts off the electricity supply automatically without turning off a switch.

Which of the following is the correct method of setting a circuit?

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?

Name one device that uses an electromagnet.

An electromagnet is a temporary magnet.

An electric bell works on the .......... effect of a current and uses an ..........

Which one of the following heater element is used in electric press

A fuse is used in an electrical appliance :

An electric bell uses ......... shaped electromagnet for its working.

Electric Current And Its Effects

Physics 1888 Views

State true or false.MCB is a safety device which cuts off the electricity supply automatically without turning off a switch.

Which of the following is the correct method of setting a circuit?

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?

Name one device that uses an electromagnet.

An electromagnet is a temporary magnet.

An electric bell works on the .......... effect of a current and uses an ..........

Which one of the following heater element is used in electric press

A fuse is used in an electrical appliance :

An electric bell uses ......... shaped electromagnet for its working.

Physics
1888 Views

State true or false.
MCB is a safety device which cuts off the electricity supply automatically without turning off a switch.