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The world is filled with The world is filled with electrical electrical chargescharges::

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What is this electrical What is this electrical potentialpotential called?called?

Static ElectricityStatic Electricity

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Static ElectricityStatic Electricity The The build upbuild up of an electric charge on the of an electric charge on the surfacesurface of an object. of an object. The charge builds up but The charge builds up but does not flow.does not flow. Static electricity is Static electricity is potential energypotential energy. It does . It does notnot move. It is move. It is storedstored..

Van de Graaff Van de Graaff generatorgenerator

Produces static Produces static electricityelectricity

Electrons are carried Electrons are carried up a rubber belt & are up a rubber belt & are transferred to the metal transferred to the metal spheresphere

The charge built up on The charge built up on the sphere is enough to the sphere is enough to send a spark several send a spark several meters through the air.meters through the air.

Static Discharge…Static Discharge…

Occurs when there is a Occurs when there is a lossloss of of static electricity due to three static electricity due to three possible things:possible things:

FrictionFriction - rubbing - rubbingConductionConduction – direct contact – direct contactInductionInduction – through an electrical – through an electrical field (not direct contact)field (not direct contact)

electric currentelectric current

continuous continuous flow of flow of electric electric charges charges through a through a materialmaterial

unit=ampunit=amp

Electricity that Electricity that movesmoves……

CurrentCurrent: The flow of electrons : The flow of electrons from one place to another.from one place to another.

Measured in Measured in amperesamperes (amps) (amps)

KineticKinetic energy energy

How can we How can we controlcontrol currents? currents?

With With circuitscircuits..CircuitCircuit: is a : is a pathpath for the flow of for the flow of

electrons. We use electrons. We use wireswires..

electric circuitelectric circuit

complete, complete, unbroken unbroken path through path through which which electric electric charges can charges can flowflow

There are 2 types of currents:There are 2 types of currents:

Direct Current (DC)Direct Current (DC) – Where – Where electrons flow in the electrons flow in the samesame direction in a wire. direction in a wire.

There are 2 types of currents:There are 2 types of currents:

Alternating Current (AC)Alternating Current (AC) – – electrons flow in electrons flow in differentdifferent directions in a wiredirections in a wire

simple circuitssimple circuits

Here is a simple electric circuit. It has a

cell, a lamp and a switch.

To make the circuit, these components are

connected together with metal connecting

wires.

cell

lamp

switch

wires

simple circuitssimple circuitsWhen the switch is closed, the lamp lights up. This is because there is a continuous path of metal for the electric current to flow around.

If there were any breaks in the circuit, the current could not flow.

circuit diagramcircuit diagram

battery

switch

lamp

wires

Scientists usually draw electric circuits using symbols;

circuit diagramscircuit diagramsIn circuit diagrams components are represented by the following symbols;

battery

switch

motorammeter

voltmeter

resistor

types of circuittypes of circuit

There are two types of electrical circuits;

SERIES CIRCUITS PARALLEL CIRCUITS

The components are connected end-to-end, one after the other.

They make a simple loop for the current to flow round.

SERIES CIRCUITS

If one bulb ‘blows’ it breaks the whole circuit and all the bulbs go out.

PARALLEL CIRCUITS

The current has a choice of routes.

The components are connected side by side.

If one bulb ‘blows’ there is still be a complete circuit to the other bulb so it stays alight.

measuring current

Electric current is measured in amps (A)

using an ammeter connected in series in the

circuit.

A

measuring currentThis is how we draw an ammeter in a circuit.

SERIES CIRCUIT PARALLEL CIRCUIT

A A

measuring currentSERIES CIRCUIT

PARALLEL CIRCUIT

• current is the same

at all points in the

circuit.

2A 2A

2A

• current is shared between the components

2A2A

1A

1A

Conductors vs. InsulatorsConductors vs. Insulators

ConductorsConductors – material through which – material through which electric current flows electric current flows easilyeasily..electrons are only loosely bound to their electrons are only loosely bound to their

atomsatoms

InsulatorsInsulators – materials through which – materials through which electric current electric current cannot movecannot move..electrons are bound tightly to their electrons are bound tightly to their

atomsatoms

ExamplesExamples

ConductorsConductors::MetalMetalWaterWater

InsulatorsInsulators::StyrofoamStyrofoamRubberRubberPlasticPlasticPaperPaper

What is Resistance?What is Resistance?

The The oppositionopposition to the flow of an to the flow of an electric current, producing electric current, producing heatheat..

The The greatergreater the resistance, the the resistance, the lessless current gets through.current gets through.

GoodGood conductors have conductors have lowlow resistance.resistance.

Measured in Measured in ohms.ohms.

What Influences Resistance?What Influences Resistance?

Material of wireMaterial of wire – aluminum and copper – aluminum and copper have low resistancehave low resistance

ThicknessThickness – the thicker the wire the – the thicker the wire the lower the resistancelower the resistance

LengthLength – shorter wire has lower – shorter wire has lower resistanceresistance

TemperatureTemperature – lower temperature has – lower temperature has lower resistancelower resistance

Factors that determine resistance of a wire

Material wire is made of

Length of Wire

Diameter of wire

Temperature of wire

What is Voltage or Potential What is Voltage or Potential Difference?Difference?

The The measure of energymeasure of energy given to the given to the charge flowing in a circuit.charge flowing in a circuit.

1.1.DifferenceDifference in electrical in electrical potentialpotential between 2 placesbetween 2 places

2.2. Causes current to flow through Causes current to flow through electric circuitelectric circuit

3.3. unit = voltunit = volt

The The greatergreater the voltage, the the voltage, the greater the force or “pressure”greater the force or “pressure” that drives the charge through the that drives the charge through the circuit.circuit.

WHAT IS VOLTAGE?WHAT IS VOLTAGE?Voltage is potential difference measured

by a ______________ ?

VOLTMETERThe unit of measure in potential difference is called the volt. For that reason, potential difference may be called voltage.

AmperageAmperage

The flow of electrons is The flow of electrons is measured in units called measured in units called amperesamperes. .

The term The term ampsamps is often used is often used for short.for short.

An An ammeterammeter is this instrument is this instrument and it is used to indicate how and it is used to indicate how many amps of current are many amps of current are flowing in an electrical circuit.flowing in an electrical circuit.

Difference between Volts and Difference between Volts and AmpsAmps

Example – you Example – you could say that…could say that…AmpsAmps measure measure

how muchhow much water water comes out of a comes out of a hose.hose.

VoltsVolts measure measure how hardhow hard the the water comes out water comes out of a hose.of a hose.

Ohm’s LawOhm’s Law Ohm's Law defines the relationships between (P) power,

(E) voltage, (I) current, and (R) resistance.

Resistance = Voltage / CurrentResistance = Voltage / Current

Ohms = Volts / AmpsOhms = Volts / Amps

Practice with Ohm’s LawPractice with Ohm’s Law

OhmsOhms VoltsVolts AmpsAmps

44 100100 2525

1515 150150 1010

22 3030 1515

99 4545 55

66 4848 88