Post on 29-Dec-2015
What is a conductor? What is an insulator?
Agenda for Tuesday Feb 22nd 1.Electricity notes/demo
All late work is due by Next Friday, March 4th
Atoms…
• Have neutronsneutrons, protonsprotons, and electronselectrons.• Protons are positivelypositively charged• Electrons are negativelynegatively charged
Electrons…
• Are located on the outerouter edges of atoms…they can be movedmoved.• A concentrationconcentration of electrons in an
atom creates a net negativenegative charge.• If electrons are strippedstripped away, the
atom becomes positivelypositively charged.
Static Electricity
• The build upbuild up of an electric charge on the surfacesurface of an object.• The charge builds up but does not does not
flow.flow.• Static electricity is potential energypotential energy.
It does notnot move. It is storedstored.
Static Discharge…
• Occurs when there is a lossloss of static electricity due to three possible things:• FrictionFriction - rubbing• ConductionConduction – direct contact• InductionInduction – through an electrical
field (not direct contact)
Electricity that moves…
• Current (Current (II)): The flow of electrons from one place to another.• Measured in amperesamperes (amps)• KineticKinetic energy
How can we control currents?
• With circuitscircuits.• CircuitCircuit: is a pathpath for the flow of
electrons. We use wireswires.
There are 2 types of currents:
• Direct Current (DC)Direct Current (DC) – Where electrons flow in the samesame direction in a wire.
There are 2 types of currents:
• Alternating Current (AC)Alternating Current (AC) – electrons flow in differentdifferent directions in a wire
There are 2 types of circuits:
• Series CircuitSeries Circuit: the components are lined up along oneone path.
• If the circuit is broken, allall ccomponents turn off
There are 2 types of circuits:
• Parallel CircuitParallel Circuit – there are severalseveral branching paths to the components
• Connected side by side
• If the circuit is broken at any one branch, only the components on that branch will only the components on that branch will turn offturn off
Conductors vs. Insulators
• ConductorsConductors – material through which electric current flows easilyeasily.
• InsulatorsInsulators – materials through which electric current cannot movecannot move.
What is current?
Agenda for Wednesday Feb 23rd 1.Ohm’s law
All late work is due by Next Friday, March 4th
Electricity that moves…
• Current (Current (II)): The flow of electrons from one place to another.• Measured in amperesamperes (amps)
What is Resistance?
• The oppositionopposition to the flow of an electric current –Can produce heatheat• More More resistance, lessless current gets
through• GoodGood conductors have lowlow resistance• Measured in ohmsohms
What Influences Resistance?
• Material of wireMaterial of wire – aluminum and copper have low resistance
• ThicknessThickness – the thicker the wire the lower the resistance
• LengthLength – shorter wire has lower resistance
• TemperatureTemperature – lower temperature has lower resistance
Potential Difference
• Work that must be done against electric forces to move a unit charge from one point to another– Charges move from negative to
positive
– Measured in volts (V)
– Car battery there is a voltage of 12 V across the negative and positive
More on Voltage?
• Voltage is the measure of energymeasure of energy given to the charge flowing in a circuit
• The greatergreater the voltage, the greatergreater the force or “pressure”the force or “pressure” that drives the charge through the circuit
Difference between Volts and Amps
• Example – you could say that…–AmpsAmps measure how muchhow much water
comes out of a hose.–VoltsVolts measure how hardhow hard the water
comes out of a hose.
Practice with Ohm’s Law
OhmsOhms VoltsVolts AmpsAmps
44 100100 2525
1515 150150 1010
22 3030 1515
99 4545 55
66 4848 88
What is an electromagnet?
• ElectromagnetElectromagnet – a magnet made from a current bearing coilcurrent bearing coil of wire wrapped around an iron or steel iron or steel core.core.
What is a generator?
• GeneratorGenerator – a machine that changes mechanicalmechanical energy to electricalelectrical energy• Usually use movingmoving magnets to
create currentscurrents in coils of wire.