What is the function of the commutator in an
electric motor?
a. it decreases the current in the coil.
b. it reverses the current in the coil.
c. it reverses the poles of the permanent
magnet.
d. it weakens the field of the permanent
magnet.

When someone slams her books on a table the kinect energy is transferred into vibrations that travel to your ears as sound waves which statement describes the movement of those waves

Why is the energy that results from a roller coaster's position at the top of a hill referred to as potential energy?

The magnitude of the poynting vector of a planar electromagnetic wave has an average value of 0.939 w/m^2 . the wave is incident upon a rectangular area, 1.5 m by 2.0 m, at right angles. how much total electromagnetic energy falls on the area during 1.0 minute?