NCERT Solutions Curiosity Chapter 7 .1 Conduction of Heat — Activity 7.1: Let us experiment
Book page 907 Updated on2026-09-05
Q1.
What will happen to the pins? Will they remain attached to the strip or will they fall?
Answer
The pins will not remain attached — all four pins will fall off, one after the other.
Why it happens: the pins are stuck to the metal strip with wax. The end of the strip away from the stand is being heated, and heat travels along the strip by conduction. When the heat reaches a pin, the wax holding that pin melts, the pin loses its grip and drops.
Check it yourself: the pins do not all fall together. That single observation is the proof that heat needs time to travel from the hot end to the cold end.
Q2.
Predict the order in which the pins will fall from the strip.
Answer
The candle is kept at the end of the strip that is away from the stand, and the pins are labelled I, II, III and IV starting from that heated end (Fig. 7.1). So the correct prediction is:
Pin I falls first (closest to the flame) then pin II then pin III and pin IV falls last (farthest from the flame)
Why this order: heat spreads outwards from the heated end. The nearer a pin is to the flame, the sooner the strip under it becomes hot enough to melt the wax. Distance, therefore, decides the order — nearest falls first.
Q3.
Record your observations in Table 7.1.
Answer
This is what the completed Table 7.1 looks like after the activity is performed.
Table 7.1: Falling of pins
Pin falling first
Reasons for what you observed
Prediction
Observation
Pin I — because it is nearest to the burning candle
Pin I fell first, followed in order by pins II, III and IV
Heat travels along the metal strip from the heated end towards the cold end by conduction. It reaches pin I first, so the wax under pin I melts first. The heat then takes more and more time to reach pins II, III and IV, which are progressively farther away.
Did you know? If you repeat the activity with the candle in the middle of the strip, the two pins on either side of the flame — equally distant from it — will fall almost together. That is the idea tested in question 1(ii) of the exercise.