Give scientific reasons for the following:
The diverged leaves of a positively charged gold leaf electroscope collapse if its disc is touched with a charge ebonite rod.

Give the scientific reason : Atoms are stable through negatively charged electron are revolving within it.

Answer in one sentence : What happens to the gold leaves when a charged object is taken near the disc of a gold leaf electroscope?

It is desired to measure the magnitude of field between the poles of a powerful loud speaker magnet.A small flat search coil of area 2cm^2 with 25 closely wound turns, is positioned normal to the field direction, and then quickly snatched out of field region. Equivalently , one can give it quick turn to bring its plane parallel to the field direction. The total charge flown in the coil (measured by a ballistic galvanometer connected to coil) is 7.5 mC.The combined resistance of coil and the galvanometer is 0.5 Omega .Estimate the field strength of magnet.