Figure 1, shows the secular variation in the magnetic dipole moment ( M ) of the
ID: 106732 • Letter: F
Question
Figure 1, shows the secular variation in the magnetic dipole moment (M) of the Earth. The straight line is the best-fit to the observations.
a) Estimate from the figure the rate of change of M with time (dM/dt,).
b) How much time is needed for M to decrease to zero?
c) What do you think will happen to the geomagnetic field when M vanishes?
d) Write briefly about the consequences on life on Earth when M vanishes?
8.7 8.60ko.............. 3 8.5 X 8.3 E 8.2 D 8.1 7.9 7.8 1850 2000 1800 1900 1950 Years AD Figure 1: Secular variation trend in the Geomagnetic dipole moment.Explanation / Answer
a)The time is plotted along x axis and dipole moment M is plotted along y axis. The rate of change of M with respect to time is dM/dt is that the dipole moment decreases as the time period increases. M and time period are inversely proportional.
b)At about 500-1000s,the value of M will entirely reach zero.
c)When M vanishes,the geomagnetic field will also slightly be affected and will decrease to some small value but not entirely zero as the earth is a natural magnet with north and south pole.
d)Earth acts as a natural magnet with north and south poles and it is said to stand on its axis which is the equator dividing it into parts. When M decreases,the magnetic stregth of earth also decreases slightly but retains some amount of magnetism in the name of residual magnetisem. The life on earth does not get affected much.