What is dynamo effect ?
A current carrying coil is placed with its axis perpendicular to $N-S$ direction. Let horizontal component of earth's magnetic field be $H_0$ and magnetic field inside the loop be $H$. If a magnet is suspended inside the loop, it makes angle $\theta $ with $H$. Then $\theta =$
A short bar magnet is placed in the magnetic meridian of the earth with north pole pointing north . Neutral points are found at a distance of $30\, cm$ from the magnet on the East - West line, drawn through the middle point of the magnet. The magnetic moment of the magnet in $Am^2$ is close to: (Given $\frac{{{\mu _0}}}{{4\pi }}\, = 10^{- 7}$ in $SI\,units$ and $B_H\, =$ Horizontal component field $= 3.6\times10^{-5}\, tesla$)
At magnetic poles of earth, angle of dip is.....$^o$
The angle between the earth's magnetic and the earth's geographical axes is....$^o$
Answer the following questions regarding earth’s magnetism:
$(a)$ A vector needs three quantities for its specification. Name the three independent quantities conventionally used to specify the earth’s magnetic field.
$(b)$ The angle of dip at a location in southern India is about $18^o$. Would you expect a greater or smaller dip angle in Britain?
$(c)$ If you made a map of magnetic field lines at Melbourne in Australia, would the lines seem to go into the ground or come out of the ground?
$(d)$ In which direction would a compass free to move in the vertical plane point to, if located right on the geomagnetic north or south pole?
$(e)$ The earth’s field, it is claimed, roughly approximates the field due to a dipole of magnetic moment $8 \times 10^{22}\; J\, T^{-1}$ located at its centre. Check the order of magnitude of this number in some way.
$(f)$ Geologists claim that besides the main magnetic $N-S$ poles, there are several local poles on the earth’s surface oriented in different directions. How is such a thing possible at all?