Question

Pins A, B, and C are attached to the iron rod with the help of wax as shown below. In which order are the pins likely to fall?​

• A. A, C, B​
• B. C, B, A​
• C. All pins will fall at the same time​
• D. A, B, C​

Answer 1

The correct option is B C, B, A​

We know that in a solid predominant mode of heat transfer is conduction and iron is a good conductor of heat. Here, Pins A, B, and C are attached to the iron rod with the help of wax.

As soon as the heat comes to the pins it will melt the wax and hence the pin will fall down. So once we find which pin felt the heat first, we can identify the order in which the pins will drop.

We know that heat always flows from a higher temperature body to a lower temperature body, here the high-temperature source(candle flame) is at the rightmost part of the rod. Initially, all the pins are at room temperature which is comparatively lower than the temperature of the flame of the candle, and hence heat from the candle flame starts to flow in the left direction (towards pins A, B, and C).

Pin C is very close to the candle flame, hence it will capture the heat first, the pin A is far away from the flame candle. Hence it will capture the heat after pin C and pin B.

So the correct order is C, B, and A.