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Current-Potential

Difference Graphs

Aim: To explain the graph shapes which

show how current changes as voltagechanges in electrical components.

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Starter

Draw a circuit diagram showing a battery

of two cells and a resistor.

Add an ammeter and a voltmeter to

measure current and voltage across theresistor.

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Starter

V

A

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Current-Potential Difference Graphs

We can plot a current-potential difference

graph for an electrical component if we

measure them and draw a graph.

Voltage, or potential difference, is the

independent variable we change this by

altering the number of cells in a battery.

Current is the dependent variable we

measure the effect that voltage has on it.

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Current-Potential Difference Graphs

Prediction

Make a prediction how do you think thecurrent will change as the voltage

changes?

Why do you think this?

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1.5V

Current-Potential Difference Model

Decrease

voltage

Increase

voltage

1.4V

0.22A

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1.5V1.5V

Current-Potential Difference Model

Decrease

voltage

Increase

voltage

2.7V

0.44A

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1.5V1.5V1.5V

Current-Potential Difference Model

Decrease

voltage

Increase

voltage

4.3V

0.68A

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1.5V1.5V1.5V1.5V

Current-Potential Difference Model

Decrease

voltage

Increase

voltage

5.9V

0.94A

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1.5V1.5V1.5V1.5V1.5V

Current-Potential Difference Model

Decrease

voltage

Increase

voltage

7.3V

1.16A

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Current-Potential Difference Graph

- Resistor

Draw a graph to show the results.

Voltage

Current

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1.5V

-1.4V

-0.22A

What if you turn the battery round?

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What if you turn the battery round?

Voltage

Current

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Why is the graph this shape?

As the voltage increases the currentincreases proportionally.

This is because the electrons are movingfaster because they are being given moreenergy.

When you turn the battery round theelectrons move in the opposite direction.

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Why is the graph this shape?

e eee

e

e

e

eee

e

1.5 V

Decrease

voltage

Increase

voltage

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Why is the graph this shape?

e eee

e

e

e

eee

e

3 V

Decrease

voltage

Increase

voltage

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Why is the graph this shape?

e eee

e

e

e

eee

e

4.5 V

Decrease

voltage

Increase

voltage

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1.5V

Current-Potential Difference Model

Decrease

voltage

Increase

voltage

1.4V

0.30A

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1.5V1.5V

Current-Potential Difference Model

Decrease

voltage

Increase

voltage

2.7V

0.55A

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1.5V1.5V1.5V

Current-Potential Difference Model

Decrease

voltage

Increase

voltage

4.3V

0.90A

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1.5V1.5V1.5V1.5V

Current-Potential Difference Model

Decrease

voltage

Increase

voltage

5.9V

1.05A

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1.5V1.5V1.5V1.5V1.5V

Current-Potential Difference Model

Decrease

voltage

Increase

voltage

7.3V

1.10A

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Current-Potential Difference Graph

- Filament lamp

Draw a graph to show the results.

Voltage

Current

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What if you turn the battery round?

Voltage

Current

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Why is the graph this shape?

As the voltage increases the currentincreases.

BUT the current increase gets smaller as

the voltage gets larger. Why? This is because the filament is heating up.

The particles in the filament are vibrating

more, meaning they get in the way of theelectrons flowing through.

This slows the electrons down resistance.

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Why is the graph this shape?

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Why is the graph this shape?

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Current-Potential Difference Graph

- Diode

Sketch the graph for these results

Voltage (V) Current (A)

7.9 97.5

6.4 76.74.9 55.9

2.4 21.3

1.4 7.3

0.9 5.50.1 0.0

-1.9 0.0

-6.4 0.0

-8.9 0.0

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Current-Potential Difference Graph

- Filament lamp

Draw a graph to show the results.

Voltage

Current

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Why is the graph this shape?

As the voltage increases the current

increases.

There are no negative values because

current can only flow one way in a diode.

The line is very steep because current can

flow very quickly in the correct direction.

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Knowledge Check

What happens to current as you increase voltage?

A It stays the same

B It increases

C It decreases

Why? The electrons are being

given more energy

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Knowledge Check

Which is the correct current-potential difference

graph for a resistor?

Voltage

Current

Voltage

Current

Voltage

Current

A B C Why?

- Current increases proportionally to potential difference

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Knowledge Check

Which is the correct current-potential difference

graph for a filament lamp?

Voltage

Current

Voltage

Current

A B C

Voltage

Current

Why?

- Current doesnt increase as fast when the lamp gets warm at a high voltage.

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Knowledge Check

Why does resistance increase in a filament lamp

as you increase the voltage?

A Electrons move slower when voltage increases.

B Electrons move slower at high temperatures.

C Particles in the wire vibrating bump into the

electrons and slow them down.

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Knowledge Check

Which is the correct current-potential difference

graph for a diode?

Voltage

Current

Voltage

Current

A B C

Voltage

Current

Why?

Current only flows in one direction It flows very fast in this direction