Objective 5 Curcuit
Investigate and compare series and parallel circuits 10th grade only
AN ELECTRICAL CIRCUIT
The circuit shown below has a power source, fuse, switch, two lamps and wires
connecting each into a loop or circle. When the connection is complete, current flows
from the positive terminal of the battery through the wire, the fuse, the switch, another
wire, the lamps, a wire and to the negative terminal of the battery. The route along which
the electricity flows is called an electrical circuit.
ELECTRICAL CIRCUIT REQUIREMENTS
A complete Electrical Circuit is required in order to make electricity practical. Electrons
must flow from and return to the power source.
There are three different circuit types, all require the same basic components:
1. Power Source is needed to supply the flow of electrons (electricity).
2. Protection Device prevents damage to the circuit in the event of a short.
3. Load Device converts the electricity into work.
4. Control Device allows the user control to turn the circuit on or off
5. Conductors provide an electrical path to and from the power source
TYPES OF CIRCUITS
Individual electrical circuits normally combine one or more resistance or load devices.
The design of the automotive electrical circuit will determine which type of circuit is
used. There are three basic types of circuits:
Series Circuit
Parallel Circuit
Series-Parallel Circuit
SERIES CIRCUITS
A series circuit is the simplest circuit. The conductors, control and protection devices,
loads, and power source are connected with only one path to ground for current flow. The
resistance of each device can be different. The same amount of current will flow through
each. The voltage across each will be different. If the path is broken, no current flows and
no part of the circuit works. Christmas tree lights are a good example; when one light
goes out the entire string stops working.
PARALLEL CIRCUIT
A parallel circuit has more than one path for current flow. The same voltage is applied
across each branch. If the load resistance in each branch is the same, the current in each
branch will be the same. If the load resistance in each branch is different, the current in
each branch will be different. If one branch is broken, current will continue flowing to the
other branches.
SERIES-PARALLEL CIRCUIT
A resistance and lamps may be connected in a circuit as illustrated below. This type of
connecting method is called series-parallel connection, and is a combination of series and
parallel connections. The interior dash board lights are a good example. By adjusting the
rheostat, you can increase or decrease the brilliance of the lights.
APPLICATIONS OF OHM'S LAW
As an application of Ohm's law, any voltage V, current I or resistance R in an electrical
circuit can be determined without actually measuring it if the two others values are
known.
This law can be used to determine the amount of current I flowing in the circuit when
voltage V is applied to resistance R. As stated previously, Ohm's law is:
Current = Voltage / Resistance.
In the following circuit, assume that resistance R is 2 and voltage V that is applied to it is
12 V. Then, current I flowing in the circuit can be determined as follows: