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

An electron falls throgh a distance of 1.5 cm in a uniform electric field of magnitude 2.0 xx10^(4) N c^(-1) the direction of the field is reversed keeping its magnitude unchanged and a proton falls through the same distance compute the time of falls in each case contrast the situation with that of free fall under gravity

A straight horizontal conducting rod of length 0.45 m and mass 60 g is suspended by two vertical wires at its ends. A current of 5.0 A is set up in the rod through the wires. (a) What magnetic field should be set up normal to the conductor in order that the tension in the wires is zero? (b) What will be the total tension in the wires if the direction of current is reversed, keeping the magnetic field same as before?

A copper rod moves parallel to the horizontal direction. The induced emf developed across its ends due to earths magnetic field will be maximum at the :

A circular coil of radius 10 cm, 500 turns and resistance 2 Omega is placed with its plane perpendicular to the horizontal component of the earth’s magnetic field. It is rotated about its vertical diameter through 180^@ in 0.25 s. Estimate the magnitudes of the emf and current induced in the coil. Horizontal component of the earth’s magnetic field at the place is 3.0 ×x 10^(-5) T.