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# Electric potential energy

Introduction to electric potential energy. Created by Sal Khan.

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• around sal says that to get the charge moving downwards, we have to exert a force of 10N. But if we exert that force in the downward direction, seeing that the metal plate is ALSO exerting a force by the same amount, won't the charge just stay stationary over there (like suspended in the electric field)???
VERY IMPORTANT • At Sal said that if we let go of the particle all of 30J would be converted to kinetic energy.
I get that if left, the particle would move away from the positively charged plate, but its still in the electric field so it should have some potential energy remaining, right? •   From the author:Yes, the 30J is really the increase in potential from it's starting point to the ending point 3 meters closer to the plate. If we let go at the ending point, the particle would start accelerating in the direction of the field (upward), and, in this case, when it passes its starting, all of that increase in potential energy will be converted to kinetic energy.

The particle, however, still has the field acting on it and will still be accelerated upwards (so you could say that it still has a positive potential relative to a point further away from the plate).
• please explain the functions of a battery.how does it function?the electrons move from - side to the bulb and to the +side? PLEASE explain it elaborately •  My understanding of the situation is that a battery has two metal plates inside along with some acid. As the metal sits in the acid, it strips protons off of one plate (zinc, for example). The plate thus builds up a negative charge, and the acid a positive charge. This positive charge in the acid begins removing electrons from the other plate (carbon, for example)causing it to have a positive charge. Thus, the two plates of metal inside the battery have different charges.

When the battery is inserted into a device and the circuit completed, the electrons can flow through the wire, evening the charge and powering the device. This process repeats until the metal in the battery has corroded from the acid (and proton/electron stripping) to a certain point, and your battery is dead.
• I got a question about electric potential energy, though may not be related to Sal's video. When a positive charge is brought near a positive point charge. The work done will be changed to the electric potential energy and stored in the charge. However, when a negative charge is brought away from the positive charge, the negative charge gains electric potential energy.When r keeps increasing, the electric potential energy stored in the negative charge will be extremely large?? Hope you guys can understand my question.... • I understand now! for opposites charges, work is done to pull them away from each other. it changes into PE and stored inside the charge. But their separation is getting larger as well, the attractive force becomes smaller, then the work needed is smaller too. So the pulling force decreases. It means that the electric PE increases at a decreasing rate!
• At Sal says that a field of 5N/C is quite strong. According to Google a Newton is about 1/5 of a pound. So the field is something like 1 pound/coloumb.

Why is this so strong? I was under the impression that a coloumb was a fairly large amount of charge. 1 pound for a high amount of charge does not seem so strong. • why does the temperature of a solid conductor increase when the conductor is carrying current? • im always confused at this fact .
if an object weighing mg newtons needs to be pulled up,it requires an opposite force EQUAL to mg newton.(should'nt the force be more than the downward force)(because if force to pull up would be equal it would be suspended in air {if applied from rest}). • The potential is constant throughout a given region of space . Is the electrical field zero or non zero   