THESE NOTES ARE PREPARED ACCORDING TO JKBOSE SYLLABI IN SIMPLIFIED AND CONCISE PATTERN
Q. 1 Fill in the blanks
a. Most liquids that conduct electricity are solutions of Acids and Bases and Salts
b. The passage of electric current through solution causes CHEMICAL effects.
c. If you pass current through the copper sulphate solution, the copper gets deposited on the plate connected to the terminal of the battery. NEGATIVE TERMINAL
d. The process of depositing a layer of any desired metal on another material by means of electricity is called. ELECTROPLATING
Q. 2 When the free end of the tester is dipped in the solution, the magnetic needle shows deflection. Can you explain the reason.
Ans: The magnetic needle shows deflection due to the current passing through the wire wound around it. This is because of magnetic effects of current.
Q. 3 Name three liquids which when tested with the tester may cause the magnetic needle to deflect.
a. Most liquids that conduct electricity are solutions of Acids and Bases and Salts
b. The passage of electric current through solution causes CHEMICAL effects.
c. If you pass current through the copper sulphate solution, the copper gets deposited on the plate connected to the terminal of the battery. NEGATIVE TERMINAL
d. The process of depositing a layer of any desired metal on another material by means of electricity is called. ELECTROPLATING
Q. 2 When the free end of the tester is dipped in the solution, the magnetic needle shows deflection. Can you explain the reason.
Ans: The magnetic needle shows deflection due to the current passing through the wire wound around it. This is because of magnetic effects of current.
Q. 3 Name three liquids which when tested with the tester may cause the magnetic needle to deflect.
Ans: The three liquids are Salt water, Lemonade and Vinegar.
Q.4 The bulb does not glow in the setup as shown in figure. List the possible reasons. Explain your answer.
Ans: There are many reasons if the bulb doesn't glow. They include:
A. Either the solution is non conducting.
B. Or the cell has not enough power to make bulb glow.
C. Besides that the circuit may be loose somewhere.
Q.5 A tester is used to check the conduction of electricity through two liquids A and B. It is found that bulb of the tester glows brightly for liquid A while it glows very dimly for liquid B. You will conclude that:
Ans:
i. liquid A is a better conductor than liquid B.
Q.6 Does pure water conduct electricity. If not what will we do to make it conducting.
Ans: Pure distilled water do not conduct electricity. To make it more conducting, we should add salt or lemon juice or acid to it.
Q. 7 In case of a fire, before a fireman uses water hoses, they shut off the mains electric supply for that area. Explain why they do this.
Ans: This is because water is good conductor of electricity. So as a safety measure, they shut off electric supply.
Q. 8 A child living in the coastal region tests the drinking water and also the sea water with his tester. He finds that compass needle deflects more in case of sea water. Can you explain the reason.
Ans: The sea water contains lot of salts than drinking water. Thus sea water is better conductor of electricity than drinking water. That is why compass needle deflects more in case of sea water.
Q.9 Is it safe for the electrician to carry electric repairs outdoors during heavy downpour? Explain.
Ans: No it is not safe for electrician to carry electric repairs outdoors during heavy downpour. This is because water is good conductor of electricity and can get electric shock.
As a safety measure, he should shut off electric supply.
Q.10 Paheli had heard that rainwater is as good as distilled water. So she collected rainwater in clean glass tumbler and tested it using tester. To her surprise she found that the compass needle shows deflection. What could be the reason.
Ans: Rainwater may contain minerals, salts, dust etc. So compass needle may show deflection.
Q. 11 Prepare the list of objects around you that are electroplated
Ans: Some objects around us that are electroplated are metal utensils, bath taps, gas burner, handles of doors etc.
Q. 12 The process that you saw in activity 8.7 is used for purification of copper. A thin plate of pure copper and think rod of impure copper are used as electrodes. Copper from impure rod is sought to be transferred to the thin copper plate. Which electrode should be attached to positive terminal of battery and why?
Ans: Since copper needs to be transferred from thick rod to thin plate. The thick impure rod should be attached to postive terminal and thin plate to negative plate.
This is because copper forms positive ions. The positive ions will move towards negative electode i.e anode to be deposited there as like charges repeal and unlike charges attract.
Q.6 Does pure water conduct electricity. If not what will we do to make it conducting.
Ans: Pure distilled water do not conduct electricity. To make it more conducting, we should add salt or lemon juice or acid to it.
Q. 7 In case of a fire, before a fireman uses water hoses, they shut off the mains electric supply for that area. Explain why they do this.
Ans: This is because water is good conductor of electricity. So as a safety measure, they shut off electric supply.
Q. 8 A child living in the coastal region tests the drinking water and also the sea water with his tester. He finds that compass needle deflects more in case of sea water. Can you explain the reason.
Ans: The sea water contains lot of salts than drinking water. Thus sea water is better conductor of electricity than drinking water. That is why compass needle deflects more in case of sea water.
Q.9 Is it safe for the electrician to carry electric repairs outdoors during heavy downpour? Explain.
Ans: No it is not safe for electrician to carry electric repairs outdoors during heavy downpour. This is because water is good conductor of electricity and can get electric shock.
As a safety measure, he should shut off electric supply.
Q.10 Paheli had heard that rainwater is as good as distilled water. So she collected rainwater in clean glass tumbler and tested it using tester. To her surprise she found that the compass needle shows deflection. What could be the reason.
Ans: Rainwater may contain minerals, salts, dust etc. So compass needle may show deflection.
Q. 11 Prepare the list of objects around you that are electroplated
Ans: Some objects around us that are electroplated are metal utensils, bath taps, gas burner, handles of doors etc.
Q. 12 The process that you saw in activity 8.7 is used for purification of copper. A thin plate of pure copper and think rod of impure copper are used as electrodes. Copper from impure rod is sought to be transferred to the thin copper plate. Which electrode should be attached to positive terminal of battery and why?
Ans: Since copper needs to be transferred from thick rod to thin plate. The thick impure rod should be attached to postive terminal and thin plate to negative plate.
This is because copper forms positive ions. The positive ions will move towards negative electode i.e anode to be deposited there as like charges repeal and unlike charges attract.
.................................
Click here for other NCERT notes.
