12th Notes

Magnetic field of earth

In this topic we will discuss about Magnetic field of earth. And also cause of earth’s magnetism, and magnetic and geographic axis and meridian.

Magnetic field of earth

In 1600 Sir William Gilbert first suggested that earth behaves like a magnet , it is huge magnet itself. The following evidence explain it-

  1. When a magnet suspended freely then it always comes in rest along the north south direction.

2.When  we put a soft iron piece under the surface of earth in the north south direction, then it acquire the properties of magnet after some time .

  1. When we draw the field lines of a magnet, we come across neutral points . At these points  magnetic field of the earth  neutralize magnetic field due to the magnet .

Cause of earth magnetism

Some important postulates are given below , but exact cause is still unknown-

  1. In 1600 William Gilbert suggested that the earth itself is a huge magnet.

2. According to Prof. Brackett , due to the rotation of earth , about its axis earth gets magnetic property , and starts behaving like a magnet. Every substance on the earth behave as a charge particle due to rotation of earth. It is a circulating currents develops due to charge particle , which are responsible for the magnetization .

  1.  As earth rotates , strong electric currents are setup due to movement of charged ions these current might be the cause of magnetization of earth.

4.Since earth core is very hot and molten which circulates the ions of Iron, Nickel in the highly conducting liquid region of the earth’s core might be forming current loops and producing earth’s magnetic field.

Important topic with Magnetic field of earth, is given below-

Straight line passes through the geographic north and south pole is called  geographic axis.  and the straight line passes through the magnetic north and south pole is called magnetic axis.

The very large circle on the earth perpendicular to the magnetic axis is called magnetic equator.

The vertical plane passing through the geographic north and south pole is called geographic meridian, and the vertical plane passing through the magnetic north and south pole is called magnetic meridian.

Next topic magnetic elements of earth-

To get the notes on magnetic elements of earth click here-