Download There is another way of determining total resistance in a parallel circuit

Equivalent resistance of parallel branches.
There is another way of determining total resistance in a
parallel circuit (but only for certain cases).
If the resistance in each branch is equal, then the
total or equivalent resistance of the branches is
equal to the resistance of one branch divided by the
number of branches.
With a parallel circuit:
Voltage remains the same for each branch.
Current will vary, based on the resistance within that branch.
To find the current for a single branch, you will need to
divide total Voltage by the Resistance for that branch.
This is more complicated if you have more than one resistor in
a particular branch.
You can check your work with this method. The
amount of current for all individual branches should
add up to the Itotal for the circuit.
For a circuit with Itotal = 3.6 Amps, you may end
up with a total of 3.56 Amps when adding the
branches separately.
Complex Circuits:
Complex circuits involve a combination of both
parallel and series circuits combined.
These are the most common circuits you will find in a
house, because they allow appliances to have
independent switches (parallel circuit), while a circuit
breaker can be wired in series to the parallel paths,
protecting the appliances from any power surge.
Electrical Safety Components
Fuses are short pieces of metal designed to melt when
too large a current passes through.
The thickness of the metal determines the amount of
current that the fuse can tolerate.
Surge Protectors and Ground Fault Interrupters
are designed to prevent excessive amounts of
electrical energy from damaging people and/or
electronic devices.
Surge protectors are used to detect voltage spikes and
then shut down the circuit to prevent damage to the
electronics.
Ground Fault Interrupters are designed to protect
from electrical shock by interrupting a household
circuit when there is a difference in the currents
between the ground wire and the "hot" wire.
A circuit breaker is an automatic switch that opens
when a circuit encounters a certain level of current.
The metal bends with the heat, causing the breaker to
open.
The circuit no longer receives current.
In order to re-set the breaker, the metal switch must
bend back into place (this happens when the
temperature falls back to a normal level).
Alternating Current (AC) and Direct (DC) Current
DC
Direct current refers to a circuit in which electrons are
flowing in only one direction (batteries).
When current begins to flow in a DC circuit, the magnetic
field builds up. During that time, the field can induce current
flow.
Once that current is flowing, the induction stops.
DC was the original circuit used by power plants, but they
could only send electricity short distances before losing
power.
AC
An alternating current source produces currents that flow in one
direction and then the other, continuously cycling from positive to
negative, and back.
Each time current direction reverses, the direction of the magnetic
field reverses. Since current alternates continuously, the magnetic
field is never static.
Power plants switched to AC circuits because they could carry
electricity hundreds of miles with little loss of power.
In addition, AC circuits (unlike DC) can be "stepped-up" or
"stepped-down" using transformers.
Transformers
Transformers are used to increase or decrease AC voltage.
Transformers consist of a "soft" metal core (usually iron)
and two sets of coiled wire.
The wire coils are arranged side-by-side, enabling the
changing magnetic field of one to overlap the field of the
other.
The number of coils in the wire determines the amount of
voltage on that side.
In the example below, the primary (input) voltage is less than
the secondary (output) voltage, so this would be a "step-up"
transformer.
A "step-down"
transformer would
have more coils on
the primary side
than the secondary.
Transformers come in handy in transmitting electricity over
long distances.
Since AC travels more efficiently at high voltages,
transformers are used to step up the voltage before the
electricity is sent out, and then other transformers are used to
step down the voltage for use in homes and businesses.