1. Power, Energy, Emf AP Physics

2. Power  Power = Δ energy / Δ time (general formula for the whole year)  This is like lifting something slowly compared with quickly  Like lifting something a short distance in 1 second vs. a large distance in 1 second  In this case, Power = Δq/ Δt (current) * V (potential difference)  P = I V  Substituting V = I R, we can also get:  P = I 2 R and P = V 2 / R

3. Internal Resistance  Emf = electromotive force = voltage  Emf with a resistor is a battery  In real life, there is some resistance inside of the battery. If the battery gives us 20V, inside it is giving us more than 20V and then losing voltage to the resistance.  When a battery fails:  Hyperphysics - http://hyperphysics.phy-astr.gsu.edu/hbase/electric/dcex6.html Emf video