ElectricityElectricityElectric Charge Electric Charge
Static ElectricityConductorsInsulatorsElectroscopeTransferring Charge
Static ElectricityStatic Electricity
Static Electricity the net accumulation of electric
charges on an object
Behavior of Charges opposite charges attract like charges repel
Static ElectricityStatic Electricity
Static Discharge the movement of
electrons to relieve a separation in charge
ConductorsConductors
Conductor material that allows electrons to
move through it easily ex: metals like copper and silver
InsulatorsInsulators
Insulator material that doesn’t allow electrons
to move through it easily ex: plastic, wood, rubber, glass
Transferring ChargeTransferring Charge
Friction Objects will either gain or lose e-
through friction, acquiring a + or – charge
Balloons Socks on carpet Car in winter Dryer
Transferring ChargeTransferring Charge
By Contact (Conduction) Touching objects can transfer charge
by creating a pathway for it to flow from one object to the other
Van De Graaff generator
Transferring ChargeTransferring Charge
Induction Transfer of charge without contact
(objects come close to one another) Wall Doorknob Van de Graaf
ElectricityElectricityElectric CurrentElectric CurrentCircuitPotential DifferenceCurrentResistanceOhm’s Law
CircuitCircuit
Circuit closed path through
which electrons can flow
Potential DifferencePotential Difference
Potential Difference (voltage) difference in electrical potential
between two places (usually the + and – terminals of a battery)
measured in volts (V)
CurrentCurrent
Current flow of electrons through a conductor measured in amperes (A)
ResistanceResistance
Resistance opposition to the flow of electrons measured in ohms ()
Copper - low resistance Tungsten - high resistance
ResistanceResistance
Resistance depends on… the conductor
wire thickness• less resistance
in thicker wires
wire length • less resistance in shorter wires
temp - less resistance at low temps
Concept Check!
If we increase resistance, what will happen to the current (flow of electrons)?
What about if we decrease resistance?
Ohm’s LawOhm’s Law
Ohm’s Law
V = I × RV: potential difference (Volts, V)
I: current (Amps, A)
R: resistance (Ohms, )
• If resistance increases, then the current decreases. • If voltage increases, then the current increases.
Ohm’s LawOhm’s LawA lightbulb with a resistance of 160 is
plugged into a 120-V outlet. What is the current flowing through the bulb?
Electrical PowerElectrical Power
Electrical Power rate at which electrical energy is converted to another form of energy
P = I × VP: power (W)
I: current (A)
V: potential difference (V)
Electrical PowerElectrical Power A calculator has a 0.01-A current flowing through it.
It operates with a potential difference of 9 V. How much power does it use?
ElectricityElectricityElectrical CircuitsElectrical CircuitsCircuit componentsSeries circuitsParallel circuitsHousehold circuits
CircuitCircuit
Circuit closed path through
which electrons can flow
Circuit ComponentsCircuit Components
A - battery C - light bulb
B - switch D - resistor
Series CircuitsSeries Circuits
Series Circuit current travels in a single path
• one break stops the flow of current current is the same throughout circuit
• lights are equal brightness each device receives a fraction of the total
voltage • get dimmer as lights are added
Parallel CircuitsParallel Circuits
Parallel Circuits current travels in multiple paths
• one break doesn’t stop flow current varies in different branches
• takes path of least resistance• “bigger” light would be dimmer
each device receives the total voltage• no change when lights are added
Household CircuitsHousehold Circuits
Combination of parallel circuits too many devices can cause wires to
overheat
Safety Features: fuse - metal melts, breaking circuit circuit breaker - bimetallic strip bends
when hot, breaking circuit
MagnetismMagnetismI. Characteristics of Magnets
Magnetism Magnetic poles Magnetic field Magnetic domain
A. MagnetismMagnetism
force of attraction or repulsion between unlike or like poles
due to the arrangement of electrons
closely related to electricity
B. Magnetic PolesMagnetic Poles
like poles repel
unlike poles attract
a broken magnet creates new poles
C. Magnetic FieldMagnetic Field
area around a magnet where magnetic forces act
field lines show direction of field (NS)
D. Magnetic DomainMagnetic Domain
groups of atoms with aligned magnetic poles
in a magnetized object, domains are all aligned
domain
MagnetismMagnetismII. Uses of Magnetic Fields
Electromagnet Speaker Motor
A. ElectromagnetElectromagnet
strong, temporary magnet formed when current is passed through a coil of wire surrounding an iron core
acts like a bar magnet when current is on
B. SpeakerSpeaker
electrical energy mechanical energy
wire coil moves back & forth as its magnetic field interacts with the field of a fixed magnet
forced vibration causes the cone to move sound
C. MotorMotor
electrical energy mechanical energy
electromagnet rotates between the poles of a fixed magnet
commutator reverses the poles of the e’magnet
C. Motor
brushes & wires to battery field magnet
armature & commutatorassembled motor
MagnetismMagnetismIII. Producing Electric Current
Electromagnetic Induction Electric Generator DC & AC Transformer
A. Electromagnetic InductionElectromagnetic Induction
producing a current by moving a wire through a magnetic field
some microphones work just like mini-speakers in reverse
sound waves cause coil to move current
Dynamic Microphone
Coil
B. Electric GeneratorElectric Generator
mechanical energy electrical energy
armature is rotated between magnet poles
magnetic field induces a current in the wire coil
MOTORGENERATOR
B. Electric Generator Hydroelectric Dam
PE of lake water is converted to KE
mechanical KE turns the generator shaft which creates electrical energy
C. DC & ACDirect Current (DC)
current flows in one direction dry cells
Alternating Current (AC) current reverses its direction
at regular intervals electrical outlets
D. TransformerTransformer
increases or decreases AC voltage primary coil AC produces a magnetic field that
induces AC in the secondary coil voltage ratio = ratio of turns in each coil
D. TransformerStep-up Transformer
increases the voltage more turns power plants
Step-down Transformer decreases the voltage fewer turns household appliances
(hairdryers, etc.)