Class 8th Science Chapter Chemical Effects of Electric Current

Class 8 Science Q&A

Class 8 Science - Chemical Effects of Electric Current

1. Fill in the blanks

(a) Most liquids that conduct electricity are solutions of acids, bases, and salts.
(b) The passage of an electric current through a solution causes chemical effects.
(c) In copper sulphate solution, copper gets deposited on the plate connected to the negative terminal.
(d) The process of depositing a layer of metal using electricity is called electroplating.

2. Why does the magnetic needle deflect when tester ends are dipped in a conducting solution?

The magnetic needle deflects because electric current flows through the solution, creating a magnetic field around the tester.

3. Name three liquids that may cause deflection in the magnetic needle in the setup.

  • Lemon juice
  • Vinegar
  • Saltwater

4. The bulb in the tester does not glow. What could be the reasons?

  • The liquid may not be a good conductor.
  • The battery may be weak or the bulb may be fused.
  • Wires may be loose or broken.

5. A tester glows brighter in liquid A than in B. What can you conclude?

(i) liquid A is a better conductor than liquid B ✅
Liquid A allows more current to pass, so the bulb glows brighter compared to liquid B.

6. Does pure water conduct electricity? If not, how can we make it conducting?

Pure water does not conduct electricity well. Adding small amounts of salt or acid makes it a good conductor.

7. Why do firemen switch off power before using water hoses?

Water can conduct electricity. Firemen switch off the main supply to prevent electric shocks during firefighting.

8. Why does the compass needle deflect more in seawater than drinking water?

Seawater contains more salts, making it a better conductor than drinking water. This causes more current and greater deflection.

9. Is it safe to repair electric lines during rain?

No, it's unsafe. Rainwater can conduct electricity and cause electric shock. Work should be done only after power is switched off.

10. Why did the rainwater cause compass needle deflection?

Rainwater may contain dissolved salts or dust from the atmosphere, making it conduct electricity and cause needle deflection.

11. Make a list of objects that are electroplated.

  • Gold-plated jewellery
  • Chrome-plated car parts
  • Silver-plated utensils
  • Nickel-plated door handles

12. In electroplating copper, which electrode is connected to the positive terminal and why?

The impure copper plate is connected to the positive terminal. It loses copper, which then deposits on the pure copper plate.

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