Chemical Effects of Electric Current — Class 8 MCQs with Answers

Chemical Effects of Electric Current — important questions & MCQs with answers (Class 8 Science)

14 solved questions from this chapter's difficulty levels, each with its answer and explanation. The other 58 are timed and scored when you sign in.

1. Q1Easy

   Liquids that allow electric current to pass through them are called:

   A.Insulators

   B.Non-conductors

   C.Magnets

   D.Good conductors✓ Correct

   Answer: D. Good conductors

   Explanation: Liquids that allow current to flow are good conductors of electricity.

2. Q2Easy

   A device often used to test whether a liquid conducts electricity is a:

   A.Thermometer

   B.Magnet

   C.Tester with an LED or bulb✓ Correct

   D.Spring balance

   Answer: C. Tester with an LED or bulb

   Explanation: A tester with an LED or bulb glows when current passes, showing the liquid conducts.

3. Q3Easy

   When current passes through a conducting solution, it can cause:

   A.A chemical change✓ Correct

   B.No change at all

   C.The liquid to freeze

   D.The liquid to vanish

   Answer: A. A chemical change

   Explanation: Passing current through a conducting solution causes chemical changes — the chemical effect of current.

4. Q4Easy

   Depositing a layer of one metal over another using electric current is called:

   A.Galvanising only

   B.Electroplating✓ Correct

   C.Welding

   D.Soldering

   Answer: B. Electroplating

   Explanation: Electroplating uses electric current to coat one metal with a layer of another metal.

5. Q5Easy

   Car bumpers and bicycle handlebars are often coated with which shiny metal by electroplating?

   A.Carbon

   B.Lead

   C.Sodium

   D.Chromium✓ Correct

   Answer: D. Chromium

   Explanation: Chromium plating gives a shiny look and protects against corrosion.

6. Q6Easy

   Which of these liquids conducts electricity?

   A.Distilled water

   B.Vegetable oil

   C.Salt solution✓ Correct

   D.Sugar solution

   Answer: C. Salt solution

   Explanation: Salt solution conducts electricity because it contains charged particles (ions).

7. Q7Medium

   Why does salt solution conduct electricity while distilled water hardly does?

   A.Dissolved salt provides ions that carry the current, which pure water lacks✓ Correct

   B.Salt is a metal wire

   C.Salt makes the water hot

   D.Distilled water is an acid

   Answer: A. Dissolved salt provides ions that carry the current, which pure water lacks

   Explanation: Salt dissolves into ions that move and carry current; pure water has too few ions to conduct well.

8. Q8Medium

   A tester bulb does not glow in a liquid, but the LED tester does. This tells us the liquid is:

   A.Magnetic

   B.A complete insulator

   C.A metal

   D.A weak conductor — it passes a small current too weak to light the bulb✓ Correct

   Answer: D. A weak conductor — it passes a small current too weak to light the bulb

   Explanation: An LED responds to weak currents, so the liquid conducts a little even when the bulb stays dark.

9. Q9Medium

   Passing current through acidified water produces gas bubbles. This is an example of:

   A.The heating effect

   B.The magnetic effect

   C.The chemical effect of electric current✓ Correct

   D.No effect

   Answer: C. The chemical effect of electric current

   Explanation: Producing gases by passing current through a solution is a chemical effect of the current.

10. Q10Medium

    In electroplating, the object to be plated is connected so that the coating metal is deposited on it. The process relies on the:

    A.Magnetic effect

    B.Chemical effect of electric current✓ Correct

    C.Heating effect only

    D.Sound effect

    Answer: B. Chemical effect of electric current

    Explanation: Electroplating deposits metal using the chemical effect of the current in a solution.

11. Q11Medium

    Why are food cans made of iron coated with tin rather than left as plain iron?

    A.Tin is magnetic

    B.Tin makes them cheaper

    C.Tin is less reactive and non-toxic, protecting the iron from rust and keeping food safe✓ Correct

    D.Tin conducts more heat

    Answer: C. Tin is less reactive and non-toxic, protecting the iron from rust and keeping food safe

    Explanation: Tin resists corrosion and is non-toxic, so it protects the iron and the stored food.

12. Q12Hard

    Assertion (A): Distilled water is a poor conductor, but salt water conducts well. Reason (R): Dissolved salt provides ions that carry the current. Choose the correct option.

    A.A is true, R is false

    B.A is false, R is true

    C.Both A and R are true and R explains A✓ Correct

    D.Both A and R are false

    Answer: C. Both A and R are true and R explains A

    Explanation: Salt water conducts because of its ions, which pure water lacks — R explains A.

13. Q13Hard

    A magnetic-needle tester deflects when current passes, even when a bulb does not glow. This is useful because it can detect:

    A.Only very strong currents

    B.Even a weak current that a bulb cannot show✓ Correct

    C.Heat only

    D.Sound only

    Answer: B. Even a weak current that a bulb cannot show

    Explanation: A magnetic-needle (or LED) tester reveals weak currents too small to light a bulb.

14. Q14Hard

    When current passes through acidified water, gas collects at both electrodes, but more at one than the other. The gases are mainly:

    A.Hydrogen and oxygen, formed by the chemical effect of current✓ Correct

    B.Carbon dioxide and nitrogen

    C.Helium and neon

    D.No gases at all

    Answer: A. Hydrogen and oxygen, formed by the chemical effect of current

    Explanation: The current splits water into hydrogen and oxygen, with more hydrogen — a chemical effect.

Chemical Effects of Electric Current — FAQs

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