Figure shows the north pole of a magnet moving away from a thick conducting loop containing a capacitor. The excess positive charge will arrive on

An observer moves towards a stationary source of sound with a velocity of one fifth of the velocity of sound. The percentage increase in the apparent frequency is

An a. c. source is connected across a pure inductor. Which one of the following figures shows the correct phase relation between the current and e.m.f.?

A disc of paper of radius ' $R$ ' has a hole of radius ' $r$ '. It is floating on a liquid of surface tension ' T '. The force of surface tension on the disc is