Current can be maintained through a pathway when
it is are attached to a source of voltage or a
battery. The voltage that the battery supplies
is call electromotive force, or emf. So when you
see an emf, just think battery and voltage.
The current moves from the positive terminal of the battery to the negative
terminal (remember the current is positively charged and is not a flow of electrons
any more.) The battery supplies the voltage which allows the "positive" particles
to move along the wire towards the negative terminal of the battery, all the
while losing their electric potential.
While a q moves along the wire with a voltage
of V, it releases qV in energy. The rate of energy
lost is measured by qV/t which equals (q/t)V.
But q/t is equal to I.
So P=IV (that one is the important formula to remember)
Right now we are going to be starting with basic circuits: a supplier of voltage
( a battery), something to use the energy (a resistor which could be anything
from a light to a computer) and wires to connect the two.
Two kinds of resistors will be set up in this
section, resistors in series and resistors in
parallel. In all of these examples the resistors
can be simplified down to one resistor.
Series: When you have resistors in series all you have to do is add
the resistance of each resistor together to discover the resistance of the circuit.
For series circuits CURRENT is always the same for each resistor. Think
of it in this way: if resistors are lined up, every electron that goes through
one resistor, must go through the next resistor.
Parallel: When you have resistors in parallel you have to use a special
formula to discover the total resistance of the circuit.
If you put the resistance of the first two circuits
in the denominator of each fraction and had the
numbers together you can discover the sum resistance
of the circuit. If you have a circuit with more
than 2 resistors in it then you must add another
fraction to the formula. VOLTAGE is always
the same for circuits in parallel.