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Current Elecricity II - Coggle Diagram
Current Elecricity II
I-V characteristics
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Method
Set up a circuit with an ammeter and resistor in series with the component, and a voltmeter in parallel
Each time, increase the voltage, and record the current
once 6-7 data points have been collected, you could measure negative value of pd and current by swapping the wires aorund
You could also re measure a point where there is a sudden change, so you can see when it happens
Plot a graph, with current on the y axis and pd on the x
Ohmic conductors
The current through an ohmic conductor is directly proportional to the potential difference across it as long as the temperature and other physical factors are constant - Ohm's law
Straight line I-V characteristic, gradient is constant
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Filament lamps
When electrical charge flows through a lamps, some energy is transferred to thermal energy
Resistance increases with temperature, as the particle have more energy, so they vibrate more, meaning its harder for electrons to pass
Less current can flow per unit of pd, so the graph gets shallower
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Diodes
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DIode will happily lets current flow through one way, where the resistance is low
if the current is revered the resistance is very high, and no current can flow
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Thermistors
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In cold conditions, the resistance increases
In hot conditions, the resistance is low
Air conditioning - As temperature rises, the resistance decreases, and the pd across the resistor increases, the increased pd supply to the air conditioning circuit helps to cool the room
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Investigating resistance
Series
Measure the current through the circuite with one resistor and calculate the resistance using the I and V measurements
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Measure the current again and calculate the resistance, keep adding identical resistors and measuring
If you plot a graph, you should see resistance and number of resistors are directly proportional
Parallel
Measure the current through the circuit in order to calculate the resistance, then add another identical resistor in parallel
Measure the total current and the pd of the battery and calculate the resistance again, then add another identical resistor
If you plot a graph you should see that the more resistors you add, the smaller the overal resistance becomes