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Transcript of The Resistance
Monday 6th November 2017
To understand the idea of resistance and its effects.
To know how to position a variable resistor in a circuit.
To vary the resistance and measure voltage and current.
To know how to draw a variable resistor in a circuit.
Units and equation
Resistance is measured in ohms, Ω. The greater the number of ohms, the greater the resistance.
The equation below shows the relationship between resistance, voltage and current:
Resistance = voltage / current
Vary the resistance and record and then voltage an current and draw a graph
Bicycles with battery operated lights often have different size bulbs for the front and rear lights. The filament in the front lamp has a resistance of 3 ohms. It takes a current of 0.6 A. What voltage does it work at?
What will happen?
An electric current flows when charged particles called electrons move through a conductor. The moving electrons can collide with the atoms of the conductor. This is called resistance and it makes it harder for current to flow. These collisions make the conductor hot. It is this that makes a lamp filament hot enough to glow.
Wach Mr Harvey
Let's set a circuit up
Watch Mr harvey
The current flowing through a resistor at a constant temperature is directly proportional to the voltage across the resistor. So, if you double the voltage, the current also doubles. This is called Ohm's Law. The graph shows what happens to the current and voltage when a resistor follows Ohm's Law.