Samacheer Kalvi 8th Science Unit 5 Book Back Answers:

Samacheer Kalvi 8th Standard New Science Book Back 1 Mark and 2 Mark Question & Answers PDF uploaded and available below. Class 8 New Syllabus 2021 to 2022 Book Back Question & Answer available for both English and Tamil Mediums. Class 8th Science Book Unit 5 – Electricity Answers/Solutions are provided on this page. 8th Std Science Book consists of 23 units, All Science Book Back One, and Two Mark Solutions are given below.

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Samacheer Kalvi 8th Science Book Back Solutions PDF:

8th Science Subject 1 Mark and 2 Mark Solutions PDF available below. Click the Download option to download the book back 1 Mark & 2 Mark questions and answers. Take the printout and use it for exam purposes. Samacheer Kalvi 8th Science Unit 5 Answers are given below.

Science Book Back Answers

Unit 5 – Electricity

I. Chosse the best answer

1. When an ebonite rod is rubbed with fur, the charge acquired by the fur is –
(a) negative
(b) positive
(c) partly positive and partly negative
(d) None of these
Answer:
(b) positive

2. The electrification of two different bodies on rubbing is because of the transfer of –
(a) neutrons
(b) protons
(c) electrons
(d) protons and neutrons
Answer:
(c) electrons

3. Which of the following a simple circuit must have?
(a) Energy Source, Battery, Load
(b) Energy Source, Wire, Load
(c) Energy Source, Wire, Switch
(d) Battery, Wire, Switch
Answer:
(d) Battery, Wire, Switch

4. An electroscope has been charged by induction with the help of charged glassrod. The charge on the electroscope is –
(a) negative
(b) positive
(c) both positive and negative
(d) None of the above
Answer:
(b) positive

5. Fuse is –
(a) a switch
(b) a wire with low resistanceFuse is
(c) a wire with high resistance
(d) a protective device for breaking an electric circuit
Answer:
(d) a protective device for breaking an electric circuit

II. Fill in the blanks

1. ……………. takes place by rubbing objects together.
2. The body which has not lost electrons becomes …………….
3. ……………. is a device that protects building from lightning strike.
4. ……………. has a thin metallic filament that melts and breaks the connection when the circuit is overheated.
5. Three bulbs are connected end to end from the battery. This connection is called …………….

Answer:

1. Transfer of electron
2. positive
3. Lightning arrestor
4. Electric fuse
5. series circuit

III. State True or False. If false, correct the statement

1. The charge acquired by an ebonite rod rubbed with a piece of flannel is negative.
Answer:
True

2. A charged body induces an opposite charge on an uncharged body when they are brought near.
Answer:
True

3. Electroscope is a device used to charge a body by induction.
Answer:
True

4. Water can conduct electricity.
Answer:
True

5. In parallel circuit, current remains the same in all components.
Answer:
False
Correct statement:
In parallel circuit, voltage remains the same in all components.

III. Match the following

1. Two similar charges                              – acquires a positive charge
2. Two dissimilar charges                         – prevents a circuit from overheating
3. When glass rod is rubbed with silk     – repel each other
4. When ebonite rod is rubbed with fur – attract each other
5. Fuse                                                           – acquires a negative charge

Answer:

1. Two similar charges                              – repel each other
2. Two dissimilar charges                        – attract each other
3. When glass rod is rubbed with silk    – acquires a positive charge
4. When ebonite rod is rubbed with fur – acquires a negative charge
5. Fuse                                                          – prevents a circuit from overheating

IV. Give reason for tile following.

1. When a glass rod is rubbed with silk cloth, both get charged.
Answer:
Reason:
When a glass rod is rubbed with a silk cloth the free electrons in the glass rod are transferred to silk cloth. It is because the free electrons in the glass rod are less tightly bound as compared to that in silk cloth. Since the glass rod looses electrons, it has a deficiency of electrons and hence acquires positive charge. But, the silk cloth has excess of electrons. So, it becomes negatively charged.

2. When a comb is rubbed with dry hair, it attracts small bits of paper.
Answer:
Reason:
Comb rubbed with hair gains electrons from the hair and becomes negatively charged. These electrons are accumulated on the surface of the comb. When a piece of paper is teared into bits, positive and negative charges are present at the edges of the bits. Negative charges in the comb attract positive charges in the bits. So, the paper bits are moving towards the comb.

3. When you touch the metal disc of an electroscope with a charged glass rod the metal leaves get diverged.
Answer:
Reason:
The leaves of an electroscope diverge because when a glass rod is touched on the metal disc, the charge travels through the metal rod to the leaves. Since, like charge repel, the charge travels till the leaves and then open up as both the leaves have like charges.

4. In an electroscope the connecting rod and the leaves are all metals.
Answer:
Reason:
These are made of metals so that the electrons become free to move.

5. One should not use an umbrella while crossing an open field during thunderstorm.
Answer:
Reason:

1. Carrying an umbrella is not advisable during thunderstorm.
2. As the rod of umbrella and its supporting wires are made up of metals.
3. Thus during thunderstorm, the conducting object should be avoided.

VI. Choose the correct answer from the following directions.

(a) If both assertion and reason are true and reason is the correct explanation of the assertion.
(b) If both assertion and reason are true and reason is not the correct explanation of assertion.
(c) If the assertion is true, but reason is false.
(d) If the assertion is false but reason is true.

1. Assertion : People struck by lightning receive a severe electrical shock.
Reason : Lightning carries very high voltage.
Answer:
(a) Both assertion and reason are true and reason is the correct explanation of assertion.

2. Assertion : It is safer to stand under a tall tree during lightning.
Reason : It will make you the target for lightning.
Answer:
(d) The assertion is false but reason is true

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