Triboelectric charging from rubbing materials

Steps:

• Identify materials' positions in the triboelectric series: polythene is electron-gaining (negative), wool is electron-losing (positive), while metals like iron and steel are conductors near neutral.
• Determine charge transfer: rubbing insulators like polythene and wool causes electrons to move from wool to polythene, creating large opposite charges.
• Evaluate conductors: iron and steel rods dissipate charge quickly due to free electrons, preventing buildup.
• Compare options: select the pair with insulators at opposite series ends for maximum charge.

Why B is correct:

• Polythene and wool are far apart in the triboelectric series, so rubbing transfers many electrons, charging polythene negatively per the series' electron affinity rule.

Why the others are wrong:

• A: Steel magnet conducts charge away, so polythene gains little net charge.
• C: Iron rod, a conductor, cannot retain the charge from wool.
• D: Both iron and steel magnet are conductors with similar series positions, yielding negligible charge transfer.

Final answer: B