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Electricity

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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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