Download Current Electricity

Current
Electricity
Current Electricity
• Current Electricity is due to
a charged electrical particle
called an Electron.
Properties of Charged
Particles
• Two or more charges that
are alike repel each other.
• Two or more charges that
are opposite attract each
other.
Current
• The charge pump creates the
FLOW of charged particles.
• This is called a CURRENT.
• Current is symbolized by
the letter I.
• It is measured in
amperes, A.
• LIKE HEAT….
• When the ends of an electric
conductor are at different
electric potentials, charge
flows from one end to the
other.
• This means there is a
potential difference, or
voltage.
• The amount of work needed
to move charges a certain
distance is known as
Voltage or Potential
Difference.
Voltage
• A measure of the energy
available to move electrons
• The electrical potential
difference between two points
• Voltage is measured like
potential energy
• Voltage drops as it gets used
Voltage Sources
• Dry Cells-Batteries
• Wet Cells
• Generators
Electric Current
• Direct Current Flows in 1 Direction
Only
• DC is produced when stored electrical
energy is tapped
• Batteries and Solar Cells have this
electrical potential
• Alternating Current changes direction
periodically
• AC is produced by a generator
Power
• A charge moving in a circuit
expends energy.
• This might result in heating the
circuit, or turning a motor.
• The rate at which electrical
energy is converted to another
form, such as mechanical, heat or
light, is called Electric Power.
• Electric Power=Current x
Voltage
=ampere x volt
watt
= watt
P
=
I
x
V
• Example 2-A 6 volt battery
delivers 0.5 A of current to
an electric motor connected
across its terminals. What is
the power of the motor?
• What energy does the motor
use in 5 minutes?
Resistance
• Resistance: Measure of how
easily current flows through a
circuit
-- higher resistance: harder for
charge to go through
-- Low Resistance: easier for
charge to go through
• Resistance increases current
goes down
• Resistance decreases current
goes up
• Resistance is measure in
Ohm’s
• Two types of resistors
--Fixed: always has the same
value
--Variable: value changes
Ohm’s Law
• OHM’S LAW
• Discovered in the 18th century
• Ratio between potential difference
and the current flowing through the
wire
• Law states: “the current that flows
through a given wire varies directly
with the applied voltage”
• Formula: I=V/R or V=IR
Ohm’s Law-Current
Flow
• Symbol for ohm is (see board); 1
ohm is the resistance which
permits a current of 1 A to flow
between a voltage of 1
• To obtain a higher voltage, higher
charge is needed; higher
voltage=electric field to be more
intense=more electrons to move
Effects of Various Electric
Current on the Body
Current in Amps
0.001
0.005
0.010
0.015
0.070
Effect
Can be felt
Painful
Muscle Spasms
Loss of Muscle Control
Fatal if longer than1 sec
Series Circuit
• Current can ONLY travel in 1
path
Series Circuit-math
• Formula to find “total resistance”
RT = R1 + R2 + etc
To find the current flow: use Ohm’s
Law
The sum of the voltage is equal to
the voltage of the entire circuit put
together
Series Circuit
• Series Circuit- break in the circuit,
stops the current
• Resistors connected in “series”,
the current travels through EACH
resistor exactly the same way
• Current encounters resistance by
each resistor; opposed by the sum
of the resistors; total resistance is
the sum
Parallel Circuit
• Current can follow many paths
Parallel Circuit
• Placing resistors in parallel
always decreases the total
resistance of the circuit!
• Total resistance decreases
because each new resistor has
a “different” path for the
electrons to flow
Parallel Circuit-Math
• Formula to find total resistance for
a parallel circuit:
1/RT = 1/R1 + 1/R2 + 1/R3 + etc
Total current is the “sum” of the
currents in the separate branches
Voltage is equal to the voltage of the
generator