Measuring Energy

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# Measuring Energy - PowerPoint PPT Presentation

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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## PowerPoint Slideshow about 'Measuring Energy' - zagiri

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Presentation Transcript

### Measuring Energy

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
• Current = Counting electrons
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 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 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 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 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 Current

Electric Current

Electric Current

Electric Current

Estimate the reading: between 150 and 200

Electric Current

Estimate the reading: between 150 and 200

What is each marking worth?

Electric Current

Estimate the reading: between 150 and 200

What is each marking worth? 5

Electric Current

Estimate the reading: between 150 and 200

What is each marking worth? 5

Electric Current

Estimate the reading: between 150 and 200

What is each marking worth? 5

Electric Current

Which scale do you use?

What is each marking worth?

Electric Current

Which scale do you use?

What is each marking worth?

Electric Current

Which scale do you use?

Estimate the reading: between? 20 and 40

What is each marking worth?

Electric Current

Which scale do you use?

Estimate the reading: between? 20 and 40

What is each marking worth? 2

Electric Current

Which scale do you use?

Estimate the reading: between? 20 and 40

What is each marking worth? 2

### Potential Difference

Potential Difference
• Potential Difference (voltage): the difference in electrical potential energy between two points in the circuit
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 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 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 Difference

looks like this...

Potential Difference

looks like this...

Potential Difference

an analogy: the waterfall

Potential Difference

an analogy: the waterfall

Current: number of electrons

Potential Difference

an analogy: the waterfall

Current: number of electrons

=amount of water

Potential Difference

an analogy: the waterfall

Current: number of electrons

=amount of water

Potential Difference: energy of the electrons

Potential Difference

an analogy: the waterfall

Current: number of electrons

=amount of water

Potential Difference: energy of the electrons

=height of the waterfall

### Resistance

Resistance
• Resistance: the ability of a material to oppose the flow of electrons through it
Resistance
• Resistance: the ability of a material to oppose the flow of electrons through it
• Ohm (Ω): the unit of electrical resistance
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 Resistance

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

Factors Affecting Resistance

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

Insulators: resist the flow of electrons

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 Resistance

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

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 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 Resistance

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

e.g. solenoid switches and furnace igniters

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 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 Law

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 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..
• 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