What it shows
The Earth has broad climate zones: the tropical zone between the Tropics of Cancer and Capricorn, the temperate zones up to the polar circles, and the polar zones. The Tropic of Cancer runs through the middle of India, so the country spans tropical and sub-tropical climates with mountains that add cold zones.
The science
Climate follows latitude because the height of the midday Sun, and so the energy received, falls from the equator to the poles. Between 23.5 degrees north and south the Sun is overhead at least once a year, giving the hot tropical zone. Between 23.5 and 66.5 degrees the Sun is never overhead and the seasons are strong, the temperate zone. Beyond 66.5 degrees the Sun does not rise for part of the year, the polar zone. Altitude, distance from the sea and winds such as the monsoon change the climate within a zone.
Materials
Cost: under Rs 200. Many items come from home or from waste; spare parts such as LEDs, motors and wire are in the store.
- A thermocol or rubber ball about 20 centimetres across
- Paints: red, green, white
- A thread and a marker for drawing latitude lines
- A stand
- Printed outline of India
- Labels
Safety
For this project: Paint in a ventilated room.
Never use mains electricity: power models with cells, batteries or a low-voltage adapter. Sharp and hot tools, flames and lab chemicals need an adult or your teacher beside you. Keep magnets, button cells and small parts away from young children, and wash your hands after making.
Step by step
8 steps. Do them in order, and test each part before you go on to the next. Write what you notice in a notebook as you go.
Mark the two poles and tie a thread round the middle of the ball as the equator; draw it with the marker.
Measure a quarter of the way from the equator to each pole, roughly 23.5 degrees, and draw the Tropics of Cancer and Capricorn.
Draw the Arctic and Antarctic circles about a quarter of the way from each pole.
Paint the tropical band red, the temperate bands green and the polar caps white.
Draw the outline of India on the globe, with the Tropic of Cancer crossing it through Gujarat, Madhya Pradesh and West Bengal.
Add small labels: hot desert in Rajasthan, wet tropical in Kerala, cold mountain in Ladakh.
Fix the ball on its stand at a tilt of 23.5 degrees.
Write a card explaining why one country can have so many climates.
What you should see
A globe with five clear bands, India correctly straddling the Tropic of Cancer, and labels showing three different Indian climates.
Viva questions
A teacher or a judge will ask how it works. Try to answer each question before you open it, then compare.
01Which latitude line passes through India?
The Tropic of Cancer, at 23.5 degrees north.
02Why is Ladakh cold although it is in the sub-tropics?
Its high altitude; air cools about 6.5 degrees for every kilometre up.
03Why does Kerala get more rain than Rajasthan?
The south-west monsoon strikes Kerala first, straight off the sea, and is forced up over the Western Ghats. The winds that reach Rajasthan are far from the sea, and the Aravalli hills run parallel to them, so they do not force the air to rise and rain.
04Where is the Sun directly overhead at noon on 21 June?
On the Tropic of Cancer.
Take it further
Add a second set of labels for five world cities and compare their climates by zone.
Change one thing, measure what happens, and add a table or chart of your readings: that is what turns a model into your own investigation.
Free ebooks for this project
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