Download Current Electricity

Friction
Contact
Induction
Current Electricity
What is the difference between static
electricity and current electricity?
Static electricity is stationary or collects on the surface of
an object, whereas current electricity is flowing very
rapidly through a conductor.
The flow of electricity in current electricity has electrical
pressure or voltage. Electric charges flow from an area
of high voltage to an area of low voltage.
Water pressure
and voltage
behave in
similar ways.
CURRENT
• The flow of charges in a circuit is called
current. Current (I) is measured in
Amperes or Amps (A).
Electricity - electrons moving through a
metal wire.
Direct current
versus
alternating current
AC vs DC:
What’s the difference?
D.C.
Electricity
Direct Current
A.C.
Alternating Current
Direct Current (DC)
• Current flows in ONE direction
• Think of water flowing in a stream
• EX. Batteries
Alternating Current (AC)
• Current flows back and forth a regular intervals
called cycles
• EX. Comes from generators and is carried to your
homes through power lines
Measured using an ammeter, unit of electric
current is ampere, A (amps)
Voltage (Potential Difference)
• Potential Energy – the energy stored in an
object
• Ex. Apple falling off a tree (converting
potential energy into motion)
– The greater the height of the apple, the greater its
potential difference
• Potential difference (voltage, V) is what causes
a current to flow in a closed circuit
• Measured using a voltmeter
Electrochemical Cells
• Ex. BATTERIES!!! – a combination of
electrochemical cells
• A package of chemicals that converts chemical
energy to electrical energy that is stored in
charged particles.
• A simple electrochemical cells includes:
– Electrolyte: a liquid/paste that conducts electricity
(ex. Citric acid)
– Electrodes: 2 metal strips that react with the
electrolyte (one will gain e-(-ve), one will lose e(+ve) (ex. zinc, copper)
2 Types of Electrochemical Cells
Wet Cell
• Uses a liquid electrolyte
• Contains two connected
plates made of different
metals or metal
compounds in a
conducting solution.
• Most car batteries have a
series of six cells, each
containing lead and lead
oxide in a sulfuric acid
solution.
2 Types of Electrochemical Cells
Dry Cell
• Uses paste instead of a
liquid electrolyte
• The zinc container of the
dry cell contains a moist
chemical paste surrounding
a carbon rod suspended in
the middle.
Term
CURRENT
VOLTAGE
Symbol
I
Definition
-
the flow of electrons through
a conductor
Amperes
(A)
-
also known as “Potential
Difference”
“push/force” of electricity
Potential energy per quantity
of electrons
Volts
(V)
V
-
RESISTANCE
R
Measured in
(Units)
measures how easily
electricity flows along a
certain path
ohm
What is electrical resistance?
Resistance (R)is the opposition to the flow of
an electric current, causing the electrical energy
to be converted to thermal energy or light.
The metal which makes up a
light bulb filament or stovetop
eye has a high electrical
resistance. This causes light
and heat to be given off.
The unit for measuring resistance is the
ohm (Ω).
What are electric circuits?
• Circuits typically contain a voltage
source, a wire conductor, and one or
more devices which use the electrical
energy.
Drawing Circuit Diagrams
Electrical Circuit Symbols
Symbol
Component
CELL, BATTERY
Function
-
Electrical source
Longer side is the
positive side
The shorter side is the
negative side
-
SWITCH
-
Opens and closes the
circuit
-
VOLTAGE
-
Measures voltage
through a device
-
AMMETER
-
Measures current
through a device
-
MOTOR
-
A type of resistor
-
(LAMP) LIGHT
-
-
RESISTOR
-
Specific load
Converts electricity to
heat and light
General load
Converts electricity to
heat
-
CONDUCTING WIRE
-
Conductor
Allows electrons to flow
Drawing Circuit Diagrams
RULES
1. Always use a ruler to draw
straight lines for the
conducting wires
2. Make right-angle corners
(∟) so that your finished
diagrams is a rectangle
• Contain 4 basic parts:
– Electrical source
– Switch
– Load
– Conducting wire
What is a series circuit?
• provides a single pathway for the current to
flow.
• If the circuit breaks, all devices using the
circuit will fail.
What is a parallel circuit?
•
has multiple pathways for the current to flow.
•
If the circuit is broken the current may pass
through other pathways and other devices will
continue to work.
Switch 1
Switch 2
Lamp 1
Lamp 2
What is the difference between an
open circuit and a closed circuit?
A closed circuit is one in which
the pathway of the electrical
current is complete and
unbroken.
An open circuit is one in which
the pathway of the electrical
current is broken. A switch is a
device in the circuit in which
the circuit can be closed
(turned on) or open (turned
off).
How is household wiring arranged?
Most household wiring is logically designed with a
combination of parallel circuits. Electrical energy
enters the home usually at a breaker box or fuse
box and distributes the electricity through multiple
circuits. A breaker box or fuse box is a safety
feature which will open.
References
• A Dercho
• Investigating Science 9 -Pearson