An electric lamp of 100 watt is used for 10 hours per day. The ‘units’of energy consumed in one day by the lamp is

A stable nucleus (light with A < 10) has

Kilowatt-hour is the unit of

Which one among the following is used to make periscope?

Potential at a point due to a point charge is V. The charge is doubled and also the distance of the point from the charge is doubled. The new potential is

A neutral (uncharged) metal ball is suspended using a non-magnetic string. A positively charged insulating rod is placed near the ball which is observed to be attracted to the rod. This is because