__________

Charge and Force

• All matter is made of atoms that contain ______________________, and protons

• Recall that protons and electrons in atoms have electric charge

• Electrons have a negative charge• Protons have a positive charge• When an object has an equal number of

protons and electrons, the object has no charge

Types of electric charge

• Protons w/ ___________ “stuck” in the nucleus

• ____________w/ ‘-’ charge freely moving around the nucleus in orbits

• Neutrons have _____________• Neutrons have no effect on the charge• Charges in objects can produce a force

between the objects• Objects are forced together or attracted

when their charges are different• “Opposite charges attract”• Same electric charges they push apart• “Like charges repel”

Electric ChargeAn electrical property of matterthat creates a __________________objects.

Depends on the imbalance of protons and electrons. i.e. net electric charge

Measured in________________, C

Every charge has an electric field that surrounds it.Electric fields exert force that causes other electric ____________________________.Any charge placed in that field will be pushed or pulled by that field.

Electric Fields• Exert a force through ___________in all directions

from the ________________• When a charged particle enters the force field of

another particle it is either_________________– The diagram represents stronger force as the lines get

closer & closer together

Electric Force

Attraction or repulsion betweenobjects due to charge______________________________________________________________

____________of Charge

Charge ________________________but it can be ______________ from object to object.

Contact Transferring charge by__________________.Induction The rearrangement of electrons on a neutral

object_______________________________

Static Electricity

• Static means ________________• Static electricity is electricity at rest• _____________ can cause it• Objects rub together and electrons move from

one object another.

Static Charge• Latin word “Stasis” which means “Stays”• Objects are typically “Neutral” w/ the same # of protons and

electrons• They can become “charged” by ________________electrons –

– NOT PROTONS! – They stay in the nucleus!• The ________________of these charges is “Static Electricity”• In Static Electricity the charges build up and STAY;

– they don’t flow as they do in electric currents

Transferring Static Charge• Friction –____________________i.e. get shocked after walking

on the carpet• Conduction –________________________contact w/ another

object – hair standing on end w/ Van de Graff machine• Induction – the force field of a highly negatively charged

object _________________away from nearby objects causing them to become + charged, they then are attracted to each other. i.e. statically charged balloon attracts small pieces of torn up paper

Conductors• Allow the _____________of electricity• _____________ electrons that are free

to move from atom to atom• metals like aluminum, gold, copper

and silver

Insulators• Insulators –_________________of electrons– hold more tightly to their ______________: – plastic, rubber, glass

Interactions between charges• same as in magnetism

– Unlike magnetism were on a magnet there is always a + on one end and a – on the other end of the magnet

– electrical charges can exist alone

• Like charges _________

• ________ charges attract

Static discharge

• Eventually static electric charge will move.• ________________may move into moisture in

the air • Or quickly in a ________.

Electric Current

• Electrons in motion.• Current: The _____________that pass a

specific point in a circuit in one second • Voltage: how ___________are being pushed.• Circuit: electric current flows through a

closed, __________________path.

Generating Electric Current

• Electrochemical cell: (battery) changes _______________________. Two types wet cell and dry cell.

• Thermocouples: a tool that uses differences in _____________________electric currents.

• Generator- next chapter but make alternating current

Types of current

• Direct current: electrons that flow in the ______________________ in a wire. (DC)

• From batteries• Alternating current: electrons that flow in

___________________in a wire. (AC)• From Genrators• Used in your home• Transformers change AC to DC

Circuits

• For current to flow there must be a complete loop

• Electric circuit: ________________path through which electrons travel.

• Electrons flow from negative to positive terminal

• Work is done if there is a resistance in the wire.

Circuits• Resistance is supplied by a resistor.• A _________________is a device that uses

electric energy to do work.• A _________________from the resistor to

the positive terminal completes the circuit.• An open __________breaks the circuit.

Two Types of Circuits

• ______________: A circuit with only one path.• All the resistors in a series circuit lie along a

single path.• The amount of current in a series circuit is the

same at all parts of the circuit.• Resistance in the circuit changes if resistors

are added or taken away.

Series Circuits• Series Circuits – provides __________for the electrons

to follow– 1. A break in the circuit stops the flow of electricity to all other

parts of the circuit– 2. With multiple light bulbs (more resistance) the current

reduces & the dimmer the lights become– 3. Ammeters should be wired in series

________________(2nd type of circuit)• Parallel circuits: The electrons in a parallel

circuit can travel through more than one path, each path is separate.

• If there’s a break in one path in the circuit, electrons can still flow through the other paths and maintain a complete circuit.

Parallel Circuits• Parallel circuits – the different parts of the circuit are on

__________ branches• A break (burn out light bulb) in the circuit doesn’t stop the

flow to the remaining devices• Multiple light bulbs will remain the same brightness since the resistance is

not decreasing as it does in a series circuit.• Each pathway can be separately switched off w/out affecting the others• Household circuits – Wired in parallel, with a standard of

120 volts• Voltmeters are wired in parallel

Parallel Circuits• The ___________________________• Water example again: added pipes coming from a

large tank will allow more water to flow out that a single pipe.– Therefore as resistance degreases, current

increases; they are inversely proportional

Schematic Diagrams (Draw the symbols and diagrams into your notes)

• All circuits need at least the following– Power supply, wire, resistors, other items include switches, connectors,

meters, etc.

• There is a set of standard symbols used to represent these items in a diagram of the circuit

Electric power and energy

• Power: The rate at which ________________ or provides energy The amount of electric power a device uses to do work is determined by its resistance.

• ______________• (P) power = (V) voltage x (I) current in the

circuit.

• Formula for energy• ________________• (E) energy used = (P) power x (t) time• The SI unit for energy is a joule.• Kilowatt-hour meters measure the electricity

used in your home.• (kWh)

Circuit Measurements• ______________- Flow of electrons through a

material• Electrical Potential –

– Similar to potential energy (lifting something higher against the force of gravity gives it greater potential_________, increasing its potential energy.)

– When given the opportunity, objects will move from higher potential energy to an area of lower potential energy

– Electrical potential is related to their electrical fields and not to height – as electrons build up on one side they “want” to flow to an____________________________

Voltage• Voltage – causes current to flow through an electrical circuit• _______– unit of measure to measure this potential• A Voltage Source (battery or generator) is required to maintain

the electrical potential in a circuit.

Electrical Current• Water flowing thru a pipe depends on more than the

angle of the pipe. It also depends on the length of the pipe, diameter of the pipe and if the pipe is clogged or open.

• Electrical Current is ____________________• Amount of Electrical Current ( amps) depends on

more than just_______, it depends on the_______________ found in the circuit.

Electrical Resistance• the opposition to the flow of electricity – • __________________– symbol is the Greek letter Omega -• Water flowing thru a pipe depends on more than the angle

of the pipe. It also depends on the length of the pipe, diameter of the pipe and if the pipe is clogged or open.

• Electricity will take the path of least resistance• The greater the resistance, the less current there is for a

given voltage.– A_____________have greater resistance than short wires– b. Thin wires have more________________ than thick wire– c. _______________have less resistance than insulators

Ohm’s Law• The relationship among

current, voltage, and resistance.

• Ohm’s law states that the _______in a circuit is equal to the ______ divided by the ________________

• I = V R

V

I R

Electric safety

• Many appliances are equipped with a _________________on the plug.

• The ground wire prevents ____________. The rounded third prong of a three-way electric plug is attached to the ground wire.

• It constantly moves static electricity from the appliance to the ground.

• Broken wires or water can cause electric appliances to short-circuit.

• A _____________occurs when electricity takes a short path and bypasses the resistors in the circuit.

• Because of this the resistance of the circuit is less and the circuit wire increases.

• The increased current can produce enough heat to melt wires and start a ______, or cause serious___________________.

Circuit protectors

• ________________protect against overloaded circuits.

• A number on the fuse indicates the max. current that will flow through it.

• Circuit breakers are often used in place of fuses. A circuit breaker is_______________ automatically when electric current in a circuit reaches its max.