Activity 4.4 Let us design and create Table 4.2 Conduction of electricity by different Class 7
hardActivity 4.4 Let us design and create Class 7
Activity 4.4 Let us design and create Class 7
Answer:
| S. No. | Object/Material | Observation (bulb glows /does not glow) | Good conductor of electricity or poor conductor of electricity |
| 1. | Piece of aluminium foil | Bulb glows | Good conductor of electricity |
| 2. | Iron nail | Bulb glows | Good conductor of electricity |
| 3. | Lump of sulfur (pea-sized) | Bulb does not glow | Poor conductor of electricity |
| 4. | Piece of coal | Bulb does not glow | Poor conductor of electricity |
| 5. | Stone | Bulb does not glow | Poor conductor of electricity |
| 7. | Piece of copper | Bulb glows | Good conductor of electricity |
Question 1.
Do you see any pattern in the glowing of bulbs when using different materials in Activity 4.4 ? Class 7
Answer:
Yes, the materials like aluminium, iron and copper allows electricity to pass through them make the bulb glow. So, they are good conductors of electricity. But the materials like sulfur, coal, stone, eraser, nylon rope and dry wood do not allow electricity to pass through them not make the bulb glow. So, they are poor conductors of electricity.
Question 2.
You would have often noticed that iron objects develop brown deposits when left in the open for a few days. In which conditions would an iron object develop brown deposits? Class 7
- When it comes into contact with dry air only.
- When it comes into contact with water only.
- When it comes into contact with both air and water.
Answer:
The iron object develops brown deposits, when it comes into contact with both air and water.
Table 4.3: Formation of brown deposit on iron nails
Answer:
Question 4.
What can you conclude from this experiment? Class 7
Answer:
Conclusion: Dry air and water alone do not produce brown deposit on iron objects. The presence of moist air (air and water) is essential for the brown deposit to be formed on iron (rusting of iron).
Question 5.
Do you know that rusting of iron is a serious problem in our country? Class 7
Answer:
Yes, every year, a very large amount of money is spent to replace or repair iron structures damaged due to rusting.