Class 8 Science Chapter 11 Question Answers - Chemical Effects of Electric Current

Q1. What is electricity?

Ans: Electricity is a phenomenon known for its effect like chemical effect, Heating effect and magnetic effect.

Q2. What is the cause of electricity?

Ans: The flow of charge is the main cause of electricity. 

Q3. What is charge?

Ans: The fundamental properties of matter caused by gain or loss of electrons.SI unit of charge is Coulomb or C.

Q4. What is the charge on 1 electron?

Ans: Charge on 1 electron = 1.6 x 10^-19C

Q5. How many electrons present in 1 coulomb charge?

Ans: Since Charge on 1 electron = 1.6 x 10^-19C

Therefore number of electrons on 1C charge =(1C)/(1.6x10^-19C) = 6x10¹⁸ electrons

Q6. What are the two types of electricity on the basis of charge?

Ans: the two types of electricity on the basis of charge are:

(a) Static electricity: The electricity cause by the charge at rest.

(b) Current electricity: The electricity cause by the charge when in motion

Q7. What is the cause of the flow of charge?

Ans: Electric potential or potential difference is the main cause of electric charge.

Q8. What do you mean by chemical effect of current?

Ans: The phenomenon of causing chemical change by passing electric current through a conduction solution is called chemical effect of current. For example: Electrolysis and Electroplating

Q9. What do you mean by heating effect of current?

Ans: Whenever current flows through a conductor it causes heating of material. This effect of current is known as heating effect of current.

Q10. What do you mean by magnetic effect of current?

Ans: Whenever current flows through a conductor it behaves like a magnet. This effect of current is known as magnetic effect of current.

Q11. What is LED?
Ans: LED stands for Light Emitting Diode. LED glows even when a weak electric current flows through it.

Q12. What precaution you should take to add LED in a circuit?

Ans: The longer lead is always connected to the positive terminal of the battery and the shorter lead is connected to the negative terminal of the battery.

Q. 13. What are good conductors?
Ans. The materials which allow electric current to pass through them are called good conductors of the electricity.

Q. 14. Give two examples of good conductors of electricity.
Ans. Copper, iron.

Q. 15. Why is it dangerous to touch an electrical appliance with wet hands?
Ans. Wet hands act as good conductors. So we feel electric shocks when we touch electric appliance with wet hands.

Q. 16. What are insulators (poor conductors) of electricity?
Ans. The materials which do not allow electric current to pass through them are called poor conductors.

Q. 17. Give two examples of poor conductors of electricity.
Ans. Dry wood, rubber.

Q. 18. What is electric current?
Ans. The flow of charges (electricity) is called electric current.

Q. 19. Do liquids conduct electricity?
Ans. Yes, liquids conduct electricity.

Q. 20. How can you check current?
Ans. We check current by using tester.

Q. 21. Give any liquid conductor.
Ans. Tap water. 

Q. 22. Can distilled water conduct electricity?
 Ans. No, distilled water cannot conduct electricity.

Q. 23. How can we test that liquids conduct electricity?
Ans. We use tester to check that the liquids conduct electricity.

Q. 24. Name some substances which make the liquids good conductor of electricity.
Ans. Acids, Bases and Salts.

Q. 25. Name two liquid substances other than water which conduct electricity.
 Ans. (i) Lemon Juice (ii) Vinegar.

Q. 26. Sometimes even though the liquid is conducting, the bulb may not glow. Give reason.
Ans. Sometimes the bulb does not glow because the current through it is too weak to make the bulb glow.

Q. 27. Which effect of current causes the bulb to glow?
Ans. Heating effect of current causes the bulb to glow.

Q. 28. Name the part of bulb which glows.
 Ans. Filament.

Q. 29. What is LED?
 Ans. LED is a device or bulb which glows even at low or small current.

Q. 30. Write full form of LED.
Ans. Light Emitting Diode.

Q. 31. What are the three effects of electric current?
Ans. There are three effects of electric current—heating, magnetic and the chemical effect.

Q. 32. What is magnetic effect of electric current?
Ans. The electric current also produces the magnetic effect by which a current carrying wire behaves like a magnet.

Q. 33 What happens when a compass needle is brought near a wire in which current is flowing?
Ans. The needle deflects.

Q. 34. How can we check magnetic effects of current?
Ans. By using magnetic compass.

Q. 35. Does distilled water conduct electricity?
 ns. No, distilled water does not conduct electricity.

Q. 36. How can we make distilled water a good conductor of electricity?
Ans. By adding some salt in distilled water.

Q. 37. What is distilled water?
Ans. The water which is free of salts is called distilled water.

Q. 38. Name a salt which makes distilled water a good conductor of electricity.
Ans. Common salt.

Q.39. What are electrodes?
Ans. The metal rods dipped in liquids to which cells are attached are called electrodes.

Q.40. Name the gases which release when current is passed through water.
Ans. Hydrogen and oxygen.

Q. 41. Name the gas deposited on negative electrode.
Ans. Hydrogen.

Q. 42. Name the gas deposited on a positively charged electrode.
Ans. Oxygen.

Q. 43. Name the process that shows the chemical effect of electricity.
Ans. Electroplating.

Q. 44. Define electroplating.
Ans. The coating of a layer of desired metal on other metallic surface by passing electric current is called electroplating.

Q. 45. Is air a conductor or an insulator?
Ans. Insulator.