4Current-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.
5Current-Potential Difference Graphs PredictionMake a prediction – how do you think the current will change as the voltage changes?Why do you think this?
6Current-Potential Difference Model 1.5V0.22ADecrease voltageIncrease voltage1.4V
7Current-Potential Difference Model 1.5V1.5V0.44ADecrease voltageIncrease voltage2.7V
8Current-Potential Difference Model 1.5V1.5V1.5V0.68ADecrease voltageIncrease voltage4.3V
9Current-Potential Difference Model 1.5V1.5V1.5V1.5V0.94ADecrease voltageIncrease voltage5.9V
10Current-Potential Difference Model 1.5V1.5V1.5V1.5V1.5V1.16ADecrease voltageIncrease voltage7.3V
11Current-Potential Difference Graph - Resistor Draw a graph to show the results.CurrentVoltage
12What if you turn the battery round? 1.5V-0.22A-1.4V
13What if you turn the battery round? CurrentVoltage
14Why is the graph this shape? As the voltage increases the current increases proportionally.This is because the electrons are moving faster because they are being given more energy.When you turn the battery round the electrons move in the opposite direction.
15Why is the graph this shape? 1.5 VeeeeeeeeeeeDecrease voltageIncrease voltage
16Why is the graph this shape? 3 VeeeeeeeeeeeDecrease voltageIncrease voltage
17Why is the graph this shape? 4.5 VeeeeeeeeeeeDecrease voltageIncrease voltage
18Current-Potential Difference Model 1.5V0.30ADecrease voltageIncrease voltage1.4V
19Current-Potential Difference Model 1.5V1.5V0.55ADecrease voltageIncrease voltage2.7V
20Current-Potential Difference Model 1.5V1.5V1.5V0.90ADecrease voltageIncrease voltage4.3V
21Current-Potential Difference Model 1.5V1.5V1.5V1.5V1.05ADecrease voltageIncrease voltage5.9V
22Current-Potential Difference Model 1.5V1.5V1.5V1.5V1.5V1.10ADecrease voltageIncrease voltage7.3V
23Current-Potential Difference Graph - Filament lamp Draw a graph to show the results.CurrentVoltage
24What if you turn the battery round? CurrentVoltage
25Why is the graph this shape? As the voltage increases the current increases.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 the electrons flowing through.This slows the electrons down – resistance.
28Current-Potential Difference Graph - Diode Sketch the graph for these resultsVoltage (V)Current (A)7.997.56.476.74.955.92.4220.127.116.11.18.104.22.168-1.9-6.4-8.9
29Current-Potential Difference Graph - Filament lamp Draw a graph to show the results.CurrentVoltage
30Why 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.
31Knowledge Check What happens to current as you increase voltage? A It stays the sameB It increasesC It decreasesWhy?– The electrons are beinggiven more energy
32Knowledge Check Which is the correct current-potential difference graph for a resistor?VoltageCurrentCurrentVoltageCurrentVoltageWhy?A B C- Current increases proportionally to potential difference
33Knowledge Check Which is the correct current-potential difference graph for a filament lamp?CurrentCurrentCurrentVoltageVoltageVoltageA B CWhy?- Current doesn’t increase as fast when the lamp gets warm at a high voltage.
34Knowledge 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 theelectrons and slow them down.
35Knowledge Check Which is the correct current-potential difference graph for a diode?CurrentVoltageCurrentCurrentVoltageVoltageA B CWhy?- Current only flows in one direction. It flows very fast in this direction.