In order to generate electricity from mechanical energy, one essential element needed to transform the energy into electrical energy is
A. an insulator
B. a magnet or a magnetic field
C. a plastic sphere
D. a light bulb

True or false: the revolution of the earth creates day and night as it rotates around the sun

You can decrease the resistance of a length of wire by

Atank has a shape of a cone with a radius at the top of 2 m and a height of 5 m. the tank also has a 1 m spout at the top of the tank. the tank is filled with water up to a height of 2 m. find the work needed to pump all the water out the top of the spout. (use 9.8 m/s2 for g and the fact that the density of water is 1000 kg/m3.)