In an ideal step down transformer, out of the following quantities, which quantity increases in the secondary coil?

An air column in a pipe, which is closed at one end will be in resonance with a vibrating tuning fork of frequency 264 Hz for various lengths. Which one of the following lengths is not possible? (V = 330 m/s)

The surface energy of a liquid drop is 'U'. It splits up into 512 equal droplets. The surface energy becomes

A rectifier is used to