☰ Contents · Physics

Earth’s magnetism and the magnetic field of current

Lessons 51–52 · 2 lessons · P.Q. Habibullayev, A. Boydedayev, A.D. Bahromov, J.E. Usarov, K.T. Suyarov, M.K. Yuldasheva. Physics, textbook for Grade 8 of general secondary schools, revised and enlarged 3rd edition. “O‘qituvchi” Publishing and Printing Creative House, Tashkent, 2019
51

The Earth’s magnetic field

Textbook: pp. 145–146
GoalKnow the Earth’s magnetic field, how magnetic poles differ from geographic poles, and magnetic storms.
New words
Earth’s magnetic field · Yer magnit maydonimagnetic declination · magnit og‘ishcompass · kompasmagnetic storm · magnit bo‘roni
Explanation

The Earth acts like a huge magnet, so there is a magnetic field around it. The Earth’s magnetic poles lie near the geographic poles, but they are not at the same points; the magnetic poles drift over time. The north end of a compass needle points toward the magnetic pole in the northern hemisphere; the needle may deviate somewhat from true north, and this deviation is called magnetic declination. The stream of charged particles from the Sun (the solar wind) is deflected by the Earth’s magnetic field, which protects the Earth’s surface. During strong solar activity the magnetic field changes strongly for a short time — this is a magnetic storm; charged particles make atmospheric gases glow near the poles (the polar lights). When finding a route, there must be no iron objects or magnets near the compass.

Worked examples
The north end of a compass needle points roughly north because it lines up along the Earth’s field line, but because of declination it may differ by a few degrees.
Charged particles of the solar wind meet the Earth’s field, bend toward the poles and make gases in the upper atmosphere glow there. So the polar lights are made by charged particles, not by “rays”.
Class activity

If you have a compass, hold it outdoors, find north and watch the needle deviate when an iron object is brought near. Write the result in your notebook.

Practice
1
Do the Earth’s magnetic poles coincide with the geographic poles?
2
What is a magnetic storm?
3
At some place the north end of a compass needle points 5° east of true north. To walk exactly to true north, which way and by how many degrees must a hiker turn from the needle’s direction?
4
Why does the Earth’s magnetic field protect living things?