Electric Circuits
Current electricity flows in electric circuits.
In a complete circuit, this
force (electromotive force, difference in potential,
Water Example of Electric Circuit
o The reservoir is the battery or other voltage source*
o Valve is a switch
Electric Current
The flow of electrons around a circuit is called
electric current.
The current (I) is measured in Amperes (Amp -
Å) by an ammeter, which is connected in series
Electric Potential Difference
Voltage is the amount of energy that is gained by each
electron from a source and lost over a load. It is the
difference in electrical potential energy between two points in a circuit.
It is measured with a voltmeter which is connected in parallel
Resistance
Resistance is the opposing force to the flow
of electrons through a part of the circuit.
Resistance (R)is the opposition to the flow of
an electric current, causing the electrical
Circuit Diagrams
Electricians and scientists
draw electric circuits using
circuit symbols.
All circuits must have at
least one source (e.g. battery), one load (e.g. light bulb) and connecting
wires between them.
Circuit diagrams use
Series Circuits
In series circuits, there is only one path for
the electrons.
Applications (Voltage)
One bulb will use the full potential difference
available at the source.
As more bulbs
are added the
Therefore
as bulbs are added in series the voltage at
the loads decreases Ex: with a 3.0 v cell
1 bulb uses all 3 v (burns bright)
2 bulbs divides 3v (each gets 1.5v, burn ½ as
bright)
Applications (current)
The rate of electric current (amps) is the
Rate of Flow
The current is the same in every load; this current is equal to
Applications (Resistance)
The overall resistance of the collection of
resistors is equal to the sum of the individual resistance values,
Activity Stations
Parallel Circuit
There is more than one path in a parallel
Applications (voltage)
Each lamp connected in parallel receives the
Applications current
As lamps are added the current flow will
Example:
1 lamp source 0.6 A branch o.6 A
2 lampssource 1.2 A branch 0.6 A
Applications (Resistance)
Resistance decreases as paths increase
Toll Booth Explanation
Adding toll booths in series
increases resistance and slows
the current flow.
Adding toll booths in parallel
Activity
Review
Value Unit SymbolUnit Physics Symbol
Voltage Volt V V
Current Amphere
(Amp) Å I
Series and Parallel Circuits Review
Series Parallel
Definition Circuit with one path for electrons to flow through
Circuit with multiple paths for electrons to flow through
Series and Parallel Circuits Summary
Series Parallel
Definition Circuit with one
path for electrons to flow through
Circuit with multiple paths for electrons to flow through
Current The same
everywhere in the circuit
Split up among the branches of the circuit
Series and Parallel Circuits Summary
Series Parallel
Definition Circuit with one path for electrons to flow through
Circuit with multiple paths for electrons to flow
through Current The same
everywhere in the circuit
Split up among the branches of the circuit
Battery Arrangements
In almost any device that uses batteries, you
do not use just one cell at a time. You normally group them together.
The batteries can be grouped together in
In series—The voltage is
increased.
In parallel—No change in
voltage; but the current
Ammeter
Ammeter is an electrical measuring device, which is used to measure electric current through the circuit.
CONNECTION OF AMMETER IN CIRCUIT
An ammeter is
always
connected in seriesto a circuit.
Voltmeter
Voltmeter is an electrical measuring device, which is used to measure potential difference between two points in a circuit.
CONNECTION OF VOLTMETER IN CIRCUIT
Voltmeter is always connected in parallel to a circuit.
SYMBOL
Activity
worksheet
Complete resistance in series and parallel
Fuses and Circuit Breakers
These devices protect circuits from over-heating due to too much current.
Fuses
Inside the fuse is a narrow wire that will melt when the current gets too high. This will break the circuit and stop the current.
Circuit Breakers
Safety with Electricity
While dealing with electricity you have to be very careful. An electric shock could
seriously hurt or kill a person.
Don’t work with electrical circuits while the power
source is on.
Avoid water while using or working with
electricity.
Avoid overloading circuits which could cause
fires.
Maintain all electrical circuits in your home.
