Actually eli6 because its not like I know nothing about electricity at all: I understand that 1 amp = 6.24\*10\^18 electrons per second and voltage is the pressure behind it. I understand that P=IV and that volts = energy per coulomb.
What I don’t understand is: (A) why power is the current multiplied by voltage and not current alone. In terms of the water analogy, the current is how much water is flowing through a pipe per second. If I’m filling a bucket with water then regardless of how much pressure and resistance there is, the only thing that matters for the bucket is how much water flows through per second, aka power which would be watts. But based on P=IV not being P=I, I know I’m wrong but I don’t know why. Why does current have to be multiplied by voltage to get the power? Is the water analogy just flawed here?
(B) How an ebike battery and system works. My ebike has 30-42v depending on SOC, but what does that mean? Does it mean that there will always be 30-42v in the motor and the wires and everything else, with the only changing thing being amps? What about amps, do they change based on voltage or in a different way? What happens to both voltage and amps when using different power settings in the display?
(C) Does ohm’s law apply to heat loss in ebikes? If yes, my current understanding is the following:
Power(heat loss) = VI = (IR)I = I²R
Power(useful kinetic energy) = VI
Wait, that would mean since both are VI, that would mean there will always be 50% useful energy and the other 50% is loss. I know this is wrong but I don’t know why. Where am I mistaken?
(D) in conclusion, is it true that an electric motor running at 2x power will have 4x the heat loss over the same duration of time? If so, what are the formulas behind it?
​
In: Physics
A) A simpler way to think of this is a ball on the bottom of a hill. The weight on the ball is current. At 0 Voltage it means the ball is at the bottom of the hill. If you let the ball go it does not move or do anything.
A better way you think of voltage is thinking how did the voltage get there? For our ball situation think of it as you roll the ball from the bottom of the hill to up the hill until you get tired. We will call this 1 unit of tiredness. The energy you used to roll it up the hill is equal to the weight of the ball and the unit of tiredness. If you let the ball go then all that energy you used to push it up the hill will make it roll down.
Voltage is potential energy, something pushed the ball up the hill and if you let it go then it will roll back down with that same energy.
For the water analogy the voltage is the pressure of the water or the height it falls from. If the water has no pressure or height then it is just a bucket of water on the ground. That will not do anything no matter how big the bucket is.
Electricity is special because there are many ways to generate that voltage and we are good at storing it in places like batteries. This is like rolling the ball up the hill and until we start the circuit it will stay up there.
Latest Answers