The capacitance depends on K, A, k and d:
Cparallel plate = K A / (4 p k d)
where K = 1 for vacuum, A = 5 cm x 5 cm = 25 cm2 = 25 x 10-4 m2, d = 2
mm = 2 x 10-3 m, and k = 9 x 109 Nt-m2/Coul2 , so C =
[(1) * (25 x 10-4 m2) ] / [4 * 3.14 * 9 x 109 Nt-m2/Co
Besides this basic equation for power:
P = I*V
remember we also have Ohms Law:
V = I*R .
Thus we can write the following equations for power:
P = I2*R = V2/R
= I*V .
To see which one gives the most insight, we need to understand what is
being held constan
We define capacitance as the amount of charge stored per volt: C = Qstored
Farad = Coulomb / Volt
Just as the capacity of a water tower depends on the size and shape, so
the capacitance of a capacitor depends on its size and shape. Just as a
Now that we have the concept of voltage, we can use this concept to
understand electric circuits.
Just like we can use pipes to carry water, we can use wires to carry
electricity. The flow of water through pipes is caused by pressure
differences, and the
If a capacitor stores charge and carries voltage, it also stores the energy it
took to separate the charge. The formula for this is:
Estored = (1/2)QV = (1/2)CV2 ,
where in the second equation we have used the relation: C = Q/V .
Note that previously we h
For a parallel plate capacitor, we can pull charge from one plate (leaving a
-Q on that plate) and deposit it on the other plate (leaving a +Q on that
plate). Because of the charge separation, we have a voltage difference
between the plates, DV.
Using C = Q/V, we see that in series the charge moved from capacitor 2s
negative plate must be moved through the battery to capacitor 1s positive
But the positive charge on the left plate of C 1 will attract a negative charge
on the right plate, an
In this first part of the course we will consider two of the common circuit
The resistor is an element that resists the flow of electricity.
The capacitor is an element that stores charge for use later (like a water
V=I*R, or R = rL/A
For parallel, both resistors are across the same voltage, so Vtotal = V1 = V2 .
The current can go through either resistor, so:
Itotal = (I1 + I2 ) .
Since the Is are in the denominator, we have:
R = Vtotal/Itotal = Vtotal/(I1+I2); or
Instead of making and storing all sizes of resistors, we can make and store
just certain values of resistors. When we need a non-standard size
resistor, we can make it by hooking two or more standard size resistors
together to make an effective resistor o