Electricity is the movement of electric charge. Electric charge can be positive or negative, and like charges repel while opposite charges attract. The amount of charge and distance between charges determine the electric force. An electric field exists around charged objects, and objects become charged through friction, conduction, or induction. Electricity can be used to power circuits, where current is the flow of electric charge. Circuits have an energy source, wires to conduct current, and a load to use the energy. Circuits can be connected in series or parallel configurations.

1. Electricity
• Charge – a physical property that can be
positive or negative
• Law of electric charge – like charges
repel, opposite charges attract
• Force between charged objects if an
electric field exist is called electric force
• 2 things affect electric force:
– Amount of charge
– Distance between the charges

2. • Electric field is the region around a charged
object
• An object becomes positively charged when it
loses electrons and negatively charged when it
gains electrons
• Objects become charged by friction,
conduction, induction
• Friction – when electrons are “wiped” from one
object to another (rubbing your hair with a
ballon)
•

3. • Conduction – electrons move from one
object to another by contact
• Induction – charges in a uncharged metal
object are rearranged without direct
contact to a charged object
• Electrical conductor – material which
allows charges to move freely
• Electrical insulator – material in which
charges can’t move freely

4. 3 ways to charge an object
Induction – no contact
Friction – rubbing
Conduction – must touch

5. • Static electricity – electric charge at rest
on an object (static – not moving)
• Electric discharge - the loss of static
electricity as the charge moves off the
object
• Electric discharges can happen quickly
with a flash of light, a shock, or a crackling
noise (lightening)

6. • Electric current - the rate at which charges
pass a given point (units amperes, A)
• AC – (alternating current) the charges
continually shift direction (plug outlets)
• DC – (direct current) the charges always move
in the same direction (battery)
• Voltage - difference between two points in a
circuit (units volts, V)
• Voltage is a measure of how much work is
needed to move a charge between two points,
the higher the voltage, the more energy released
per charge (9V, 12V, 120V, 220V)

7. • Resistance - the opposition to the flow of
charges (units ohms,Ω (R))
• The higher the resistance, the lower the
current
• Resistance depends on the material,
length, thickness and temperature
• Superconductor – super cooled material
that lowers resistance (magnets)

8. • Machines can change one form of energy
to another (conversion)
• Thermocouples change thermal energy
into electric energy and photocells change
light energy to electric energy
• Electric circuits are complete closed paths
that allows electric charges to flow

9. • Three parts to a circuit are:
• 1. Energy source (provides electric
charge)
• 2. Wires (allows charge to flow from point
to point)
• 3. Load (changes electric energy into
other forms of energy)
• EX: radio – electrical to sound

10. Batteries (power source)
Dry Cell Wet Cell

11. • Two types of circuits: series and parallel
• Series: all parts are connects in a single
loop in a one way path
• All current must pass through the
complete series for circuit to work
• Any interruption causes the circuit to fail
(Xmas lights)
• Useful in burglar alarms

12. Series Ciruit

13. • Parallel: loads are connected side by side
and current can travel on more than one
path
• When circuit is interrupted, circuit
continues to function regardless
• Homes are wired on parallel circuits and
can have different loads in the circuit

14. Parallel Circuit

15. • Circuit failures are usually caused by over
loads or damage to the structure of the
circuit
• Fuses and circuit breaks “fail over” and
automatically break the circuit to protect
circuit and property

16. • Electromagnets – temporary magnets that lose
their magnetism when electric current is
removed
• Electricity can produce magnet fields and can
cause metals such as iron and steel to act like
magnets
• Generator is a device that converts mechanical
energy into electrical energy by using magnets
and a coil of wire that creates magnetic fields

17. • Electric motors convert electrical energy
into mechanical energy that is used to do
work
• EX: motors in house hold appliances like
blenders and washing machines