B H tan I H ( . ) (i) At magnetic equator The Earth’s magnetic field is parallel to the surface of the Earth (i.e., horizontal) which implies that the needle of magnetic compass rests horizontally at an angle of dip, I = o . B H = B E B V = This implies that the horizontal component is maximum and vertical component is zero at the equator. (ii) At magnetic poles The Earth’s magnetic field is perpendicular to the surface of the Earth (i.e., vertical) which implies that the needle of magnetic compass rests vertically at an angle of dip, I = o .
Hence, B H = B V = B E This implies that the vertical component is maximum at poles and horizontal component is zero at poles. EXAMPLE . The horizontal component and vertical component of Earth’s magnetic field at a place are . G and .
G respectively. Calculate the angle of dip and resultant magnetic field. (G-gauss, cgs unit for magnetic field 1G = – T) Solution: B H = . G and B V = .
G tan tan ( . ⇒= The resultant magnetic field of the Earth is H . G 12th - 12th - - - - - Unit Magnetism and magnetic effects of electric current Aurora Borealis and Aurora Australis People living at high latitude regions (near Arctic or Antarctic) might experience dazzling coloured natural lights across the night sky. This ethereal display on the sky is known as aurora borealis (northern lights) or aurora australis (southern lights).
These lights are often called as polar lights. The lights are seen above the magnetic poles of the northern and southern hemispheres. They are called as “Aurora borealis” in the north and “Aurora australis” in the south. This occurs as a result of interaction between the gaseous particles in the Earth’s atmosphere with highly charged particles released from the Sun’s atmosphere through solar wind.
These particles emit light due to