Multiple select
which of the following discoveries are attributed to johannes kepler? select all that apply.
the orbits of the planets are ellipses.
the earth is round.
gravitational forces govern planetary motion.
all planets move in elliptical orbits with the sun at one focus.
a line connecting a planet to the sun sweeps out equal areas in equal time periods.

stands for electromotive force and it is measured in volts. despite its name, it is not actually the force in the sense of being a "pushing" or "pulling" (not measured in newtons).an equation that relates emf,  ℰ,  to a battery's terminal voltage, v, current, i, and internal resistance, r, is    ℰ = v + irin this case, the emf can be interpreted as a voltage—a difference in electric potential.i would not say that it would be considered an energy. if emf can be defined as the energy/work per a unit charge from a battery or other electric source, then it is not strictly energy.