⚡ Chemical Effects of Electric Current – MCQs for Class 8 Science

Part 2: Q26–Q50

Q26. Which among the following is a poor conductor of electricity?

A) Tap water
B) Distilled water
C) Lemon juice
D) Salt solution

✅ Correct Answer: B) Distilled water

Explanation:

• B) ✔ Pure water lacks ions, so it is a poor conductor.
• A, C, D contain ions → good conductors.

Q27. Which of the following statements about LED as a tester is true?

A) LED glows only in AC circuit
B) LED glows only when small current passes
C) LED glows even without current
D) LED cannot be used as tester

✅ Correct Answer: B) LED glows only when small current passes

Explanation:

• B) ✔ LEDs are sensitive to small currents and glow in test circuits.

Q28. Electrolysis of water requires adding a small amount of:

A) Sugar
B) Salt
C) Oil
D) Alcohol

✅ Correct Answer: B) Salt

Explanation:

• B) ✔ Adding salt (NaCl) provides ions, making water conductive.

Q29. Which metal is commonly electroplated on car parts and taps for shine and resistance?

A) Zinc
B) Chromium
C) Copper
D) Aluminium

✅ Correct Answer: B) Chromium

Explanation:

• B) ✔ Chromium gives a shiny, corrosion-resistant finish.

Q30. Which effect of electric current is responsible for electroplating?

A) Heating effect
B) Magnetic effect
C) Chemical effect
D) None of these

✅ Correct Answer: C) Chemical effect

Explanation:

• C) ✔ Electroplating = deposition due to chemical effect of current.

Q31. The process of purifying metals using electricity is called:

A) Refining
B) Electrolysis
C) Electrorefining
D) Both A and C

✅ Correct Answer: D) Both A and C

Explanation:

• D) ✔ Electrorefining is an application of electrolysis for metal purification.

Q32. Which of the following is NOT a use of electroplating?

A) Prevent corrosion
B) Increase thickness of object
C) Improve appearance
D) Make jewelry attractive

✅ Correct Answer: B) Increase thickness of object

Explanation:

• B) ✔ Electroplating deposits only a thin layer, not thickness.

Q33. In electrolysis, positive ions move towards:

A) Cathode
B) Anode
C) Both electrodes
D) None

✅ Correct Answer: A) Cathode

Explanation:

• A) ✔ Positive ions (cations) are attracted to negative electrode.

Q34. During electrolysis of water, the ratio of hydrogen to oxygen collected is:

A) 1:1
B) 2:1
C) 3:1
D) 4:1

✅ Correct Answer: B) 2:1

Explanation:

• B) ✔ Water → 2H₂ : O₂ → ratio = 2:1.

Q35. Electroplating of metals is done to:

A) Make them heavier
B) Improve appearance and prevent corrosion
C) Reduce cost of production
D) Remove impurities

✅ Correct Answer: B) Improve appearance and prevent corrosion

Explanation:

• B) ✔ Electroplating provides shine and protection.

Q36. Which electrode is used for depositing metal during electroplating?

A) Anode
B) Cathode
C) Both
D) None

✅ Correct Answer: B) Cathode

Explanation:

• B) ✔ Cathode (negative electrode) attracts metal ions.

Q37. Which of the following solutions will conduct electricity best?

A) Sugar solution
B) Salt solution
C) Kerosene
D) Distilled water

✅ Correct Answer: B) Salt solution

Explanation:

• B) ✔ Salt solution ionizes → excellent conductor.

Q38. Why does a bulb not glow when circuit is connected with distilled water?

A) Because of too much resistance
B) Because distilled water is a poor conductor
C) Because distilled water is a conductor
D) Because bulb is fused

✅ Correct Answer: B) Because distilled water is a poor conductor

Explanation:

• B) ✔ No ions → negligible current → bulb won’t glow.

Q39. The passage of electric current through a solution is known as:

A) Electroplating
B) Electrolysis
C) Electrorefining
D) Conduction

✅ Correct Answer: B) Electrolysis

Explanation:

• B) ✔ Electrolysis = decomposition of electrolyte by current.

Q40. Which one of the following is a conductor of electricity?

A) Alcohol
B) Tap water
C) Kerosene
D) Distilled water

✅ Correct Answer: B) Tap water

Explanation:

• B) ✔ Contains dissolved salts/ions → conducts electricity.

Q41. The solution that allows electric current to pass through is called:

A) Electrolyte
B) Insulator
C) Superconductor
D) None

✅ Correct Answer: A) Electrolyte

Explanation:

• A) ✔ Electrolytes = ionic solutions (acids, bases, salts).

Q42. What is deposited on cathode during electrolysis of copper sulphate?

A) Sulphur
B) Oxygen
C) Copper
D) Hydrogen

✅ Correct Answer: C) Copper

Explanation:

• C) ✔ Cu²⁺ ions deposit on cathode.

Q43. Which of the following does NOT conduct electricity?

A) Vinegar
B) Kerosene
C) Lemon juice
D) Salt water

✅ Correct Answer: B) Kerosene

Explanation:

• B) ✔ Kerosene is non-polar and lacks ions.

Q44. Electroplating of cheap ornaments is done with:

A) Nickel
B) Copper
C) Silver/Gold
D) Zinc

✅ Correct Answer: C) Silver/Gold

Explanation:

• C) ✔ To make them attractive and shiny.

Q45. Which effect of electric current is used in electric bell?

A) Magnetic effect
B) Chemical effect
C) Heating effect
D) None

✅ Correct Answer: A) Magnetic effect

Explanation:

• A) ✔ Current magnetizes coil → attracts hammer → bell rings.

Q46. In the tester, the bulb glows due to:

A) Magnetic field
B) Heating effect of current
C) Reflection of light
D) None

✅ Correct Answer: B) Heating effect of current

Explanation:

• B) ✔ Current heats filament → it glows.

Q47. The electrolyte used in electroplating of iron with copper is:

A) Silver nitrate solution
B) Copper sulphate solution
C) Zinc sulphate solution
D) Sodium chloride solution

✅ Correct Answer: B) Copper sulphate solution

Explanation:

• B) ✔ Provides Cu²⁺ ions for deposition on iron.

Q48. Which of the following is NOT a result of chemical effect of current?

A) Bubbles formation
B) Change in colour of solution
C) Deposition of metals
D) Production of heat in wire

✅ Correct Answer: D) Production of heat in wire

Explanation:

• D) ✔ Heat is a heating effect, not a chemical effect.

Q49. Electroplating of tin is done on food cans to:

A) Make them lighter
B) Prevent corrosion and rusting
C) Make them attractive
D) Increase cost

✅ Correct Answer: B) Prevent corrosion and rusting

Explanation:

• B) ✔ Tin layer protects iron can from rusting.

Q50. Which electrode loses metal during electroplating?

A) Cathode
B) Anode
C) Both
D) None

✅ Correct Answer: B) Anode

Explanation:

• B) ✔ Metal from anode dissolves → deposited on cathode.

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