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Ncert Exemplar Solutions Class 7 Science Electric Current and Its Effects
Welcome to NCTB Solutions. Here with this post we are going to help 7th class students for the Solutions of NCERT Exemplar Class 7 Science Book, Unit 14, Electric Current and Its Effects. Here students can easily find step by step solutions of all the problems for Electric Current and Its Effects, Also here our Science teacher’s are solved all the questions with easily understandable language with proper guidance so that all the students can understand easily.
Electric Current and Its Effects all Question Solutions :
Multiple Choice Questions :
Question no – (1)
When an electric current flows through a copper wire AB as shown in Figure 14.1, the wire
The correct answer is option – (a)
The wire deflects a magnetic needle placed near it.
Question no – (2)
Choose the statement which is not correct in the case of an electric fuse.
The appropriate answer is option – (c)
There is a minimum limit on the current which can safely flow in the electric circuits.
Question no – (3)
Three bulbs A, B, C are connected in a circuit as shown in Figure 14.2. When the switch is ‘ON’
The answer is alternative – (c)
When the switch is ‘ON’ all the bulbs A,B and C will glow at the same time.
Question no – (4)
When a switch is in OFF position
The correct option is – (b) (ii) and (iii) are correct
When a switch is in OFF position circuit is open and no current flows through it.
Question no – (5)
Which of the following precautions need not be taken while using electric gadgets/appliances/circuit?
The correct answer is alternative – (d)
We should never turn the switch in ON position.
Very Short Answer Questions :
Question no – (6)
The conducting metal usually have a low melting point because of which when large electric currents passes through the circuit , the fuse melts breaking of the circuit thus preventing any possible fire.
Question no – (7)
The devices which we use these days in place of fuses are MCB or Miniature Circuit Breaker. It is made automatically switch off when an unsafe amount of electricity passes through it.
Question no – (8)
(i) Our body is a good of electricity.
(ii) An electric cell produces electricity from the Chemicals in it.
(iii) In an electric circuit a fuse is a Safety device to prevent possible fire
(iv) A combination of two or more cells is called a Battery.
Question no – (9)
(i) TBTAYER → Battery.
(ii) SFEU → Fuse.
(iii) HTRCO → Torch.
(iv) HICWTS → Switch.
Question no – (10)
No, the steps taken by Paheli were absolutely wrong because the continuous passing of electricity through the bulb will heat up the bulb which may start to burn up the towel and cause fire in the room.
Question no – (11)
These days Compact Florescent Lamps are preferred over bulbs as bulb uses a lot of electricity out of which some gets wasted in the form of heat and on the other hand CFL uses little electricity to produce light and with no wasting of electricity.
Question no – (12)
An electric fuse is required in all electrical appliances as it will prevent any possible short circuit or damages to the electrical appliances in the circuit by breaking off the current that is passing through it.
Short Answer Questions :
Question no – (13)
No, we must not use the same fuse in a geyser and a television set because a geyser and television both have different limit to which they can bear the electricity passing through it. So it is advised to use different fuses for different appliances.
Question no – (14)
(i) The devices in which the heating effect of current is used are iron machine and geyser.
(ii) The devices in which the magnetic effect of current is used are fans and electric bell.
Question no – (15)
We cover pinholes which are within the reach of children because a children may try to puts his finger in the pinholes and may get a electrical shock that he is unable to bear.
Question no – (16)
The electromagnet made by Paheli will attract more pins because it is a quite known fact that the more turns a electromagnet has the more is the electromagnetic effect of that electromagnet. The electromagnet made by Paheli had 100 turns while the electromagnet made by Boojho had 50 turns.
Long Answer Questions :
Question no – (18)
(i) No, the heat produced in both the wire will be different. The heat that will be produced in a wire depends upon the length and the thickness of the wire that is being used. Since they are using wire of same thickness but different length it means that Paheli’s 10 cm wire will be heated much more than Boojho’s 5 cm wire.
(ii) If the wire were of the same length but different thicknesses then the heat produced in the wire would still be different heat produced in a wire also depends on the thickness of the wire that is being used.
Question no – (19)
An electric bell consists of a wire wound around an iron piece. An iron strip with a hammer and a contact screw is placed close to the coil .When the iron strip comes in contact with the contact screw, electricity passes through the coil and it magnetizes the coil. The magnetized coil pulls the iron strip that has a hammer at one end towards the gong and this strike produces the sound. When the hammer hits the gong the circuit breaks which demagnetizes the coil and so the strip returns to its original place. After the strip returns to its place the circuit again becomes complete and hammer hits again and again tills the switch is pressed.
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