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Measuring Energy. Electric Current. Electric Current. Current: the rate of flow of electrons past a certain point in a circuit. Electric Current. Current: the rate of flow of electrons past a certain point in a circuit C urrent = C ounting electrons. Electric Current.

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electric current1
Electric Current
  • Current: the rate of flow of electrons past a certain point in a circuit
electric current2
Electric Current
  • Current: the rate of flow of electrons past a certain point in a circuit
    • Current = Counting electrons
electric current3
Electric Current
  • Current: the rate of flow of electrons past a certain point in a circuit
    • Current = Counting electrons
  • Ampere (A): the unit of electric current
electric current4
Electric Current
  • Current: the rate of flow of electrons past a certain point in a circuit
    • Current = Counting electrons
  • Ampere (A): the unit of electric current
      • e.g. a 15A breaker opens the circuit

when there are 15A of

electrons flowing through

the wires

electric current5
Electric Current
  • Current: the rate of flow of electrons past a certain point in a circuit
    • Current = Counting electrons
  • Ammeter: a device used to measure current
electric current6
Electric Current
  • Current: the rate of flow of electrons past a certain point in a circuit
    • Current = Counting electrons
  • Ammeter: a device used to measure current
    • -an ammeter is always placed in series
electric current7
Electric Current
  • Current: the rate of flow of electrons past a certain point in a circuit
    • Current = Counting electrons
  • Ammeter: a device used to measure current
    • -an ammeter is always placed in series
slide10

Electric Current

Which scale do you read?

slide11

Electric Current

Which scale do you read?

slide12

Electric Current

Estimate the reading:

slide13

Electric Current

Estimate the reading: between 150 and 200

slide14

Electric Current

Estimate the reading: between 150 and 200

What is each marking worth?

slide15

Electric Current

Estimate the reading: between 150 and 200

What is each marking worth? 5

slide16

Electric Current

Estimate the reading: between 150 and 200

What is each marking worth? 5

Final Answer?

slide17

Electric Current

Estimate the reading: between 150 and 200

What is each marking worth? 5

Final Answer? 175

slide18

Electric Current

Which scale do you use?

Estimate the reading: between?

What is each marking worth?

Final Answer?

slide19

Electric Current

Which scale do you use?

Estimate the reading: between?

What is each marking worth?

Final Answer?

slide20

Electric Current

Which scale do you use?

Estimate the reading: between? 20 and 40

What is each marking worth?

Final Answer?

slide21

Electric Current

Which scale do you use?

Estimate the reading: between? 20 and 40

What is each marking worth? 2

Final Answer?

slide22

Electric Current

Which scale do you use?

Estimate the reading: between? 20 and 40

What is each marking worth? 2

Final Answer? 32

potential difference1
Potential Difference
  • Potential Difference (voltage): the difference in electrical potential energy between two points in the circuit
potential difference2
Potential Difference
  • Potential Difference (voltage): the difference in electrical potential energy between two points in the circuit
  • Volt (V): the unit of potential difference
potential difference3
Potential Difference
  • Potential Difference (voltage): the difference in electrical potential energy between two points in the circuit
  • Volt (V): the unit of potential difference
  • Voltmeter: a device used to

measure potential difference

potential difference4
Potential Difference
  • Potential Difference (voltage): the difference in electrical potential energy between two points in the circuit
  • Volt (V): the unit of potential difference
    • a voltmeter has to be connected in a parallel circuit
potential difference5
Potential Difference

looks like this...

potential difference6
Potential Difference

looks like this...

slide30

Potential Difference

an analogy: the waterfall

slide31

Potential Difference

an analogy: the waterfall

Current: number of electrons

slide32

Potential Difference

an analogy: the waterfall

Current: number of electrons

=amount of water

slide33

Potential Difference

an analogy: the waterfall

Current: number of electrons

=amount of water

Potential Difference: energy of the electrons

slide34

Potential Difference

an analogy: the waterfall

Current: number of electrons

=amount of water

Potential Difference: energy of the electrons

=height of the waterfall

resistance1
Resistance
  • Resistance: the ability of a material to oppose the flow of electrons through it
resistance2
Resistance
  • Resistance: the ability of a material to oppose the flow of electrons through it
  • Ohm (Ω): the unit of electrical resistance
resistance3
Resistance
  • Resistance: the ability of a material to oppose the flow of electrons through it
  • Ohm (Ω): the unit of electrical resistance
  • Ohmeter: a device used to measure electrical resistance
factors affecting resistance1
Factors Affecting Resistance

1. Type of Material: some materials have less internal resistance than others

factors affecting resistance2
Factors Affecting Resistance

1. Type of Material: some materials have less internal resistance than others

Insulators: resist the flow of electrons

factors affecting resistance3
Factors Affecting Resistance

1. Type of Material: some materials have less internal resistance than others

Insulators: resist the flow of electrons

e.g. air plastic

factors affecting resistance4
Factors Affecting Resistance

2. Length: the longer a wire is, the more electrical resistance the wire has

factors affecting resistance5
Factors Affecting Resistance

2. Length: the longer a wire is, the more electrical resistance the wire has

High voltage transmission lines: are used

so fewer electrons have to travel through wires travelling long distances

factors affecting resistance6
Factors Affecting Resistance

3. Thickness: a thick wire has less electrical resistance than a thin one.

e.g. extension cords shouldn't be used permanently because they are usually thinner wires and can overheat

factors affecting resistance7
Factors Affecting Resistance

4. Temperature: as temperature increases, its electrical resistance increases

e.g. solenoid switches and furnace igniters

factors affecting resistance8
Factors Affecting Resistance

4. Temperature: as temperature increases, its electrical resistance increases

e.g. solenoid switches and furnace igniters

-if igniter heats up, its resistance increases

factors affecting resistance9
Factors Affecting Resistance

4. Temperature: as temperature increases, its electrical resistance increases

e.g. solenoid switches and furnace igniters

-if igniter heats up, its resistance increases

-solenoid opens and gas is released & furnace lights

ohm s law1
Ohm’s Law
  • In 1827, Georg Ohm noticed a relationship between current, potential difference and resistance
  • After many experiments he noted that:
    • For a given resistance, as the electric potential difference across a load increases, so does the current
ohm s law2
Ohm’s Law
  • Ohm’s Law- the relationship between resistance, current and potential difference.
    • For a given potential difference, as the resistance increases, the current decreases
another way to look at resistance
Another way to look at resistance..
  • The flow of electrons can be compared to people running an obstacle course
    • More obstacles= runners moving slower through the course
    • Wider course=more runner able to go through at the same time
electron flow link
Electron flow link
  • The amount of resistance in a circuit affects the amount of current(electrons) that can flow through it
    • More obstacles, slower flow of electrons
    • Wider= more electrons can flow through
    • # of loads= more loads means more resistance
factors that can increase resistance
Factors that can increase resistance
  • Connecting more loads in series
  • Connecting loads in series rather than parallel
  • Making the conductor longer
  • Making the conductor thinner
  • Using material with a high resistance