Electricity MCQs

Q1. Why is the tungsten used almost exclusively for filament of electric lamps?

• A.Tungsten has a high melting point
• B.Tungsten is a good conductor of electricity
• C.Tungsten is non-toxic
• D.Tungsten is cheap

Answer: A. Tungsten has a high melting point

NCERT fact (physics, chapter 'Electricity'): Tungsten's high melting point makes it suitable for lamp filaments. Why option A fits - Tungsten's high melting point allows it to withstand the high temperatures inside the lamp. Distractor analysis: option B) 'Tungsten is a good conductor of electricity' misses the point - This is not the primary reason tungsten is used for lamp filaments; option C) 'Tungsten is non-toxic' is wrong because This is not a relevant characteristic for lamp filaments. Final answer - A) Tungsten has a high melting point.

Q2. In the electrolytic refining of a metal M, what should be used as the anode, the cathode and the electrolyte?

• A.Anode: impure metal M; Cathode: thin strip of pure metal M; Electrolyte: a water-soluble salt solution of metal M
• B.Anode: pure metal M; Cathode: impure metal M; Electrolyte: pure water
• C.Anode: carbon; Cathode: carbon; Electrolyte: metal M
• D.Anode: any non-metal; Cathode: any non-metal; Electrolyte: water

Answer: A. Anode: impure metal M; Cathode: thin strip of pure metal M; Electrolyte: a water-soluble salt solution of metal M

Q3. What is the function of an earth wire? Why is it necessary to earth metallic appliances?

• A.To provide a path for the current to flow safely to the ground.
• B.To provide a path for the current to flow to the live wire.
• C.To provide a path for the current to flow to the neutral wire.
• D.To provide a path for the current to flow to the ground without any resistance.

Answer: A. To provide a path for the current to flow safely to the ground.