Rundown Of Electrostatics
Let’s zoom in.
“Positive” and “negative” charges are actually kind of abstract. What exactly do these charges mean? Well…they kind of mean nothing. If I remember correctly, while Benjamin Franklin started developing hypotheses about electricity, a way to differentiate between two charges became mandatory. What better way than a “plus” and “minus.”
Although electrons and protons have a massive difference in the their masses, the charges are equal and opposite. e = (+/-)1.6E-19. Therefore, the charge of a particle will be the number of electrons it carries times the electric charge. If we happen to be measuring in moles, we take that number and multiply it by 6.02E23 atoms.
Let’s play God and place an electron 10nm away from a proton (that’s a huge space). What will be the magnitude and direction of the electrostatic force that they feel? (Remember that Newton’s 3rd Law states the force will be the SAME, not the acceleration. Since the mass of the electron is much smaller than the proton, the electron will accelerate towards it. The force that attracts these two charges was defined by some guy named Coulomb. He said that the force is proportional to some constant (k = 9.0E9 N*m^2/C^2), as well as the magnitude of the two charges q1,q1. Remember q=n(e). The force is also going to be inversely proportional to the square of the distance (r) between the two charges.
F=kqQ/r^2
Now, what happens if we take away one of the charges. The equation turns into F=kq/r^2. This equation defines the electric field magnitude. This is simple. A single charge (what is called a source charge) will create an electric field purely because of its charge. Any extra charge that happens to roam in it’s field (the distance is still r^2) will feel that magnitude.
If we wanted to define the FORCE is feels, we simply can derive it from Newton’s Second Law F=ma = qE where “q” is the charge” and E is the electric field magnitude we just defined. Solving for acceleration, we find that it becomes a = qE/m.
I’ll type about electrostatic potential energy tomorrow.
