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NCERT Solutions Curiosity Chapter 7 .3.1 Clinical thermometer — In-text Questions

Book page 1287 Updated on2026-09-05

Q1.
The normal temperature of a healthy human body is taken to be 37.0 °C. But in this activity, did you find that the normal temperature of every person was 37.0 °C? Or did you find the temperature slightly higher or lower for some people?
Answer

No, every person did not read exactly 37.0 °C. Some readings were a little higher and some a little lower — in the sample table above they ranged from about 36.6 °C to 37.3 °C, all of these being perfectly healthy children.

Why it happens: 37.0 °C is not a rule that every body must obey. It is the average body temperature of a large number of healthy people. Since it is an average, most healthy people lie a little on either side of it.

The body temperature of a person is influenced by:

  • Age — small children usually a little higher, old people a little lower;
  • Time of the day — usually lowest in the early morning, highest in the evening;
  • Activity level — higher just after running or playing.

Whatever these variations, human body temperature does not normally go below 35 °C or above 42 °C.

Try This: Measure your own temperature at the same three times every day (say 7 am, 1 pm and 7 pm) for a month and write the readings in your notebook. You will see a small daily rise and fall of a few tenths of a degree — even though you were healthy all month.
Q2.
Do small children generally have slightly higher body temperatures as compared to adults?
Answer

Yes. Small children generally have a body temperature that is a little higher than that of adults — often a few tenths of a degree Celsius above the adult average.

Why it happens: a small child’s body is more active in building itself up, so it produces heat faster for its size. At the same time a child is small, so the body must keep a slightly higher temperature to balance the heat it loses. This is normal and is not fever.
Tip: Because the difference is small, do not call it fever from touch. Measure it. Doctors usually treat a reading clearly above 38 °C as fever, whatever the age.
Q3.
Do old people, even when healthy, generally have lower body temperatures than young adults?
Answer

Yes. Healthy old people generally show a body temperature that is slightly lower than that of young adults.

Why it happens: as age advances, the body produces heat a little more slowly and controls its temperature slightly less sharply. So the “normal” value shifts a little downward — again by a few tenths of a degree Celsius, not by whole degrees.

This is why the book says a perfectly healthy person may have a normal temperature slightly different from 37.0 °C, and lists age as one of the factors that influence it.

Did you know? For very small children and for old people, the digital thermometer may also be placed in the armpit. A reading taken this way is about 0.5 °C to 1 °C lower than the actual body temperature, so that much has to be allowed for.
Q4.
I have seen a friend of mine using a digital thermometer that reads temperature on a different scale. It shows the normal temperature of a healthy human body as 98.6 °F. What is the reason for this difference?
Answer

Because that thermometer is showing the same temperature on a different scale — the Fahrenheit scale, whose unit is degree Fahrenheit, written °F.

Normal body temperature
= 37.0 °C on the Celsius scale
= 98.6 °F on the Fahrenheit scale
Same hotness — two different numbers, because the two scales are marked differently.
Why it happens: a scale is only a set of marks that somebody chose. On the Celsius scale, melting ice is marked 0 and boiling water is marked 100, so there are 100 steps between them. On the Fahrenheit scale the same two points are marked 32 and 212, so there are 180 steps between them. A Fahrenheit degree is therefore a smaller step than a Celsius degree, and the numbers come out bigger.

It is like measuring the same cloth in metres and in centimetres — 1.5 m and 150 cm are the same length written two ways.

Did you know? There is a third scale used in scientific work, the Kelvin scale, whose unit is the kelvin (K) — and the kelvin is the SI unit of temperature. Temperature in K = temperature in °C + 273.15, so 37.0 °C = 37.0 + 273.15 = 310.15 K. Note that the degree sign is not written with K.
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