The earth may have even reversed the direction of its field several times during its history of 4 to 5 billion years. How can geologists know about the earth's field in such distant past?

An electron falls from rest through a vertical distance h in a uniform and vertically upward directed electric field E. The direction of electric field is now reversed, keeping its magnitude the same. A proton is allowed to fall from rest in it through the same vertical distance h. The time of fall of the electron, in comparison to the time of fall of the proton is

A short magnet of magnetic moment 5.25xx10^(-2) JT^(-1) is placed with its axis perpendicular to the earth's field direction. At what distance from the centre of the magnet on (i) its normal bisector (ii) its axis, is the resultant field inclined at 45^@ with the earth's field. Magnitude of the earth's field at the place is 0.42G. Ignore length of the magnet in comparison to the distances involved.

At a place ,the vertical component of earth's magnetic field is sqrt(3) times its horizontal component . What will be the angle of dip at that place ?

A man can jump up to a height of 1.5 m on the earth's surface. What should be the radius of a planet having the same average density as that of the earth so that the man can come out of the gravitational field of that planet in one jump ? Radius of the earth is 6400 km.

A short bar magnet of magnetic moment 5.25xx10^(-2)J.T^(-1) is placed with its axis perpendicular to the earth's magnetic field . At what distance from the centre of the magnet , the magnet , the resultant field is inclined at 45^(@) with the earth's field on its axis Ignore the length of the magnet in comparison to the distance involved .