NCERT Class VII Science Solutions: Chapter 4 – Heat Part 5

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Question 19:

Observe the picture given as Figure. Water is being boiled in a pan of wide base.

As showing in images is a Water is being boiled

Water is Being Boiled

As showing in images is a Water is being boiled

  1. Which position P or T will feel warmer?

  2. Fill up the boxes P and T to indicate the mode of flow of heat to the hand.

Answer:

Position ‘P’ will feel warmer due to the hot air rising up

P – Convection process because the air near the boiling water gets not and rises.

T – Radiation because air does not feel as hot as at the top.

Question 20:

Look at Figure.

The length of wire PQ in case of A is equal to the diameter of the semicircle formed by the wire CDE, in case B. One pin is attached to each wire with the help of wax as shown in figure. Which pin will fall first? Explain.

As showing in images is a which pin will fall first

Which Pin Will Fall First

As showing in images is a which pin will fall first

Answer:

The pin on the wire PQ in case A will fall first because the heat will reach to the pin on straight wire PQ before the heat reaches the pin on the semicircular wire CDE in case B.

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