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## Electricity

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### electricity chapter 1 – PowerPoint PPT presentation

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Title: Electricity

1
Electricity
• Chapter 1

2
Electric Charge
• Charges Exert Force
• Atoms are composed of particles with ______.
The law of electric charges states that like
charges _____and opposite charges _______

3
The Force Between Protons and Electrons
• Protons and electrons have ________ charges, they
are ________ to each other

4
The Electric Force and the Electric Field
• _____________ the force of attraction or
repulsion on a charged particle that is due to an
electric field
•
• ____________ the space around a charged object
in which another charged object experiences an
electric force

5
Charge it!
• Friction
• Conduction
• ________- occurs when electrons are wiped
• from one object to another
•
•
• __________ electrons move from one object to
another by direct contact.
•

6
Charge it!
• _________ charges in an uncharged metal object
are rearranged without direct contact with a
charged object

7
Conservation of Charge
• When you charge something by any method,
____________________________________. The numbers
of ________ and _______ stay the same.
• Detecting Charge
• You can use a device called an _____________ to
see if something is charged

8
Moving Charges
• __________- a material in which charges can move
easily
• Examples
• __________- a material in which charges
• cannot move freely
• Examples

9
Static Electricity
• _________________ electric charge at rest
produced from friction or induction
• _________________ the release of electricity
stored in a source

10
1.2 Electric Current Energy
• _______________ rate at which charges pass a
given point
• When you flip a switch, an _____________ is set
up in the wire at the speed of light. The
electric field causes the _________ in the wire
to move.
• This electric field is created so quickly that
all electrons start moving through the wire
_________.
• Think of the electric field as a command to the
electrons to charge ahead.

11
Types Electric current
• Direct Current (DC)
• Alternating Current (Ac)
• ___________________ charges always flow in one
direction.
• Ex
• ___________________ charges shift
• from flowing in one direction to
flowing in
• the reverse direction
• EX

12
Voltage and Energy
• _______ the potential difference between points
• SI unit
•
• You can think of voltage as the amount of energy
released as a charge moves between two points in
the path of a current.
• As long as there is a voltage between _________,
charges will flow in the wire. The ____ of the
current depends on the _______

13
Varying Nature of Voltage
• Different devices need different levels of
voltage.
• 1.5 V 9 V
12 V

14
Resistance
• ___________ opposition to the flow of electric
charge
• SI unit
• Good conductors, such as copper, have
_____________
• Poor conductors, such as iron, have
______________
• Resistance depends on thickness, length,
temperature
• Thick, _____ wires have ____ resistance than
____, thin wires.
• The resistance of metals _________ as temperature
_________

15
Resistance
16
Generating Electrical Energy
• Remember energy is not created or destroyed it
only changes forms
• Parts of a Cell
• A cell contains a mixture of chemicals called an
__________. Every cell also has a pair of
__________made from conducting materials

17
Types of Cells
• There are 2 types of cells
• ___ have an electrolyte
• Example batteries sulfuric acid is the
electrolyte
• ___ have a dry electrolyte
• Example small radios or flashlights

18
Generating Electrical Energy
• Cells change chemical or radiant energy into
electrical energy. Batteries are made of one or
more cells.
• ____________ can take thermal energy and transfer
it to electrical energy.
• _________convert light energy into electrical
energy.

19
1.3 Electrical Calculations
• How fast is a nanosecond? A nanosecond (ns) is
one-billionth of a second. Electrical signals
travel at 30 cm/ns. Calculate how far electrical
signals travel in 1 second.
•

20
Connecting Current, Voltage, and Resistance
• Georg Ohm Ohm (1789 1854) studied the resistance
of materials. He measured the current that
resulted from different voltages applied to a
piece of metal wire.
• Ohms Law the ratio or voltage (V) to current
(I) is the resistance (R) of a material
• V I x R

Electric Power
Unit SI Unit
Voltage (V) V - volt
Current (I) A- Amps
Resistance (R) Ohm - ?
21
Ohms Law Calculations
• Ex 1 What is the voltage if the current is 2 A
and the resistance is 12 ? ?
• Ex 2 Find the voltage if the current is 0.2 A
and the resistance is 2 ?

22
Ohms Law Calculations
• Ex 3 The resistance of an object is 4 ?. If the
current in the object is 9 A, what is the voltage
used?
• Ex 4 An object has a resistance of 20 ?.
Calculate the voltage needed to produce a current
of 0.5 A.

23
Electric Power
• Electrical Power (P) the rate at which
electrical energy is converted into other forms
of energy
• Si Unit Watts (W)
• Power voltage x current
• P V x I

Unit SI Unit
Voltage (V) V - volt
Current (I) A- Amps
Power (P) W - Watts
24
Electrical Power Calculations
• Ex 1 A toaster draws approximately 10 A of
current. A home receives 120 V at each electrical
outlet. What is the power of the toaster?
• Ex 2 A car uses a 12 V battery. One headlight
draws 3.0 A. What is the power of the headlight?

25
Electrical Power Calculations
• EX 3 A light bulb draws a 0.5 A current at a
voltage of 120 V. What is the power rating of the
light bulb?

26
Electrical Energy
• Measuring Household Energy Use
• Different amounts of electrical energy are used
each day in a home. Electric companies usually
calculate electrical energy by multiplying the
power in kilowatts by the time in hours.

27
1.4 Electric Circuit
• Just like a roller coaster, an electric circuit
always forms a loop it _____ and ____ at the
____ place
• Parts of an Electric Circuit
• (light bulb, appliance)

28
Switches
• Sometimes, a circuit also contains a _____
• _____ opens or closes a circuit
• _____ electrons can ____
• _____ electrons _____________

29
Types of Circuits
• ______________ a circuit in which the parts are
joined one after another such that the current in
each part is the same.
• _________for charges to follow charges must
flow through each part of the circuit
• The voltage across each load is _________

Series circuits are useful in wiring burglar
alarms. If any part of the circuit fails, there
will be __________in the system and the alarm
will sound.
30
Types of circuits
• _______________- a circuit in which the parts are
joined in branches so that the voltage (potential
difference) across each part is the same
• Loads do ___have the _________________
• Charges have more than ___ path to follow

Parallel Circuits are used in almost all
appliances and decorative string lights
31
Household circuit safety
• Circuits can ____ if they are __________ or a
wire breaks or has water damage.
• To prevent fire
• A thin strip of metal in circuit that the charges
flow through.
• If the current is too high, the metal will
melt and the circuit
• is broken
• A switch that automatically opens if the current
is too high. A metal strip heats up, bends, and
opens the switch stopping the flow of current
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