The efficiency of a machine is the ratio between the output power and the power in input:

in our problem, the output power is 3760 W while the input power is 4000 W, so the efficiency is

So the efficiency of the machine is 94%.
Oppositely charged objects form in induction but not in conduction.
Explanation :
In Newton's prism experiment, a ray of white sunlight is passed to the prism. It is observed that the light gets refracted at different angles and different colors spread.
Sunlight is made up of seven colors. The colors are the same as the colors seen in the rainbow. The colors are :
- Violet
- Indigo
- Blue
- Green
- Yellow
- Orange
- Red
So, the correct option is (c) " White sunlight is made up of all the colors of the visible spectrum ".
The hydrometer displays the density of the liquid you stick it in, COMPARED TO WATER.
If you stick it in pure water, it should read 1.00 . This is a good way to check your hydrometer and see whether it's reading correctly ("calibrated").