Download ch19 electricity notes

Name: _________________________
Period: ____________
Ch.19 notes: Electric Charges and Currents:
I. Electricity
A. Subatomic particles and electricity
1. Only the _________________ loosely held in the outermost shells of atoms are involved
in producing electricity.
a. ____________________ = negatively charged particles found orbiting the nucleus of
atoms flowing through circuits.
b. ____________________ = positively charged particles found in the nucleus of atoms;
do not flow through circuits.
2. Most atoms of elements are _____________________ meaning that they have the same
number of protons as _____________________________.
3. Atoms of elements can be made to be charged by stripping away its electrons which
would make the atom __________________________ charged.
4. Like electric charges ___________________ and unlike charges _____________________.
B. ___________________ electricity = buildup of electric charges on an object or electric
charges at rest.
1. ______________________________ = a device with two metal leaves that spread apart
when a charged object touches the metal knob showing that like charges ______________.
2. A Wimshurst generator and ___________________________ generator are both used to
produce static electricity.
3. _________________________ = a violent discharge of static electricity (50,000 volts).
a. ___________________ = results from rapid expansion of heated air caused by lightning.
b. _________________________ suggested that lightning is a form of static electricity and
then proceeded to invent the lightning rod which works according to the principle of
_______________________ = a connection from the part of a circuit to a moist,
highly conductive earth to prevent possible electrical accidents.
II. Electrical terms:
A. _______________________ = the push or drive that forces electrons through a circuit or
“the potential difference” that exists between two terminals.
1. The higher the voltage, the __________ energy each electron carries.
2. The standard unit of voltage is the ______________ (V).
B. ___________________ = the flow of electrons through wires. (Symbol is ______).
1. The higher the electric current, the ______________ the amount of electrons flowing
passed a given point per second.
2. The standard unit of electric current is called a(n) _____________________.
a. one _______________ = 6.24 x 10 18 electrons flowing passed a given point per second.
(symbol is an A).
C. ____________________ = the opposition to the flow of electricity (Symbol is _______).
1. The standard unit of __________________ is the ___________ (Formula symbol is ____).
2. The resistance of a wire is dependent up on the make-up of wire:
a. __________________ is used in most circuits because it’s a great conductor and thus has
very ___________ resistance.
3. ____________ Law = the current is equal to the voltage ÷ resistance.
Current = voltage
Resistance
or I = V
R
Ex. What is the current going through a load which has a resistance of 60 ohms and a
voltage of 120 volts? Answer: ________ amperes
a. If the voltage is increased, then the current will _______________________.
b. If the resistance is increased, then the current will _____________________.
III. Direct Current (D.C.) vs. Alternating Current (A.C.)
A. _________________ current = one way trip of electricity from the negative terminal to the
positive terminal.
1. The current is produced by _____________________ used to operate small appliances.
2. The scientist who developed the first chemical-electric wet cell or battery was
Allesandro ____________________.
a. electric current flows from the _____________ terminal to the ____________ terminal.
B. ____________________ current = electrons move back-and-forth in wires changing
direction on a regular basis.
1. Type produced by generating stations or ___________________________.
2. Can be transmitted over _________ long distances.
3. Alternating current reverses direction at _________ cycles/second or _______ Hertz.
IV. Parts of a circuit:
A. Terms:
1. __________________= the part of a circuit you want to operate. Ex. Hair dryer, lamp, etc.
a. the first light bulb was invented by __________________________.
b. the symbol for a light bulb is a ______________.
2. ___________________ = the part of a circuit that produces the electric current.
a. Ex. Outlet, generator, or battery.
3. ___________________ = another name for a “complete circuit”
4. ___________________ = a circuit that will not operate a load because of a ___________ =
an opening or gap in a circuit that does not allow electrons to flow.
a. ________________ = a device which is a type of circuit-breaker because it lets electrons
flow if closed and stops flow when open.
b. _________________ - ________________ = a bimetallic strip that acts like a switch
because it bends outward when overheated thus opening a circuit and is placed in circuits
to prevent electrical fires.
c. ____________________ = a metal strip that melts when a short circuit or overload exists
in wires opening a circuit and also is used to prevent electrical fires.
5. ______________________ = a device that is added to a circuit to reduce electric current
flow. (Symbol is ___________ ).
B. Types of Circuits: (Series vs. paralllel circuit)
1. _____________________ = circuit in which all the loads are connected one after another.
a. would not operate any of the loads if a __________________ were to occur anywhere.
b. the more and more loads that are added, such as light bulbs, the ______________ power
each receives thus the lights gets dimmer. Ex. Old Xmas tree ______________.
2. _____________________ = circuit in which the current divides equally between two or
more loads on separate branches.
a. the type used in most _____________________ circuitry.
b. other loads will still operate if there is a break and each load gets full voltage.
V. Electric __________________ = the measure of the rate at which electricity does work or
provides energy.
A. Electric ___________________ is measured in units called __________________.
1. ______________ = the measure of how fast energy is being transferred in a circuit, or the
amount of power an appliance consumes.
2. _____________________ = equal to 1000 watts and is used in calculating electric bills.
Power = voltage x ___________________ or P = V x I
(watts) (volts)
(amperes)
Ex. How much power does a light consume if a 12 volts battery delivers a current of 5 amps?
Answer: _____________________
3. Most small appliances in the household operate on ________ volts found in most outlets,
while larger appliances such as stoves/dryers operate on __________ volts.
B. Electric ________________ = Power x time; PPL electric companies base bill on this.
1. So if PPL is charging 10 cents per kilowatt hour, record bill below:
VI. Electrical Safety:
A. Ways to avoid electrical fires and other hazards:
1. Do not _____________________ a circuit – over-heating of wires due to too many
appliances plugged into an outlet drawing more energy than a circuit could deliver.
2. Do not create a ____________-circuit = when a circuit is bypassed causing a lower
resistance and thus increases current causing over-heating of wires.
a. can happen if have frayed wires, placing cords under rugs, touching 2 wires, etc.
3. Do not stick metallic objects into _________________ to get out broken plugs.
4. Do not handle appliances when your hands are wet or while standing in water, such as
taking showers or down-electrical lines.