One end of a long wire is fixed while a vibrator is attached to the other end. When the vibrator is energized, the types of waves generated in the wire are

The main reason for making the cover of a vacuum flask airtight is to prevent heat loss by

A radio is operated by eight cells each of e.m.f. 2.0V connected in series. If two of the cells are wrongly connected, the net e.m.f. of the radio is

If a charged ion goes through combined electric and magnetic fields, the resultant emergent velocity of the ion is