Equipment REQUIRED PRACTICAL – This will need 2 lessons including drawing the graph and concluding. Electric circuit boxes Voltmeters Ammeters Resistance wire meter rulers Crocodile clips See if students can remember the measurement of energy

Resistance and Ohm’s Law State Ohm’s law and describe its conditions. Measure the effect of changing the length of a wire on its resistance in a controlled experiment Rearrange equations for resistance and potential difference. 4 6 8

Starter – Literacy Task resistance is a mesure of how hard its for a current to flow through a component in a circuit resistors are added into a circuit to reduce the amount of curent flowing. The bigger the value of resistence, the lower the current. Components such as bulbs have resistance. Wen more bulbs are added too a series circuit resistance increases. This causes the current to decrease. There are 10 errors to correct Print or

Starter – Make The corrections Resistance is a measure of how hard it is for a current to flow through a component in a circuit. Resistors are added into a circuit to reduce the amount of current flowing. The bigger the value of resistance, the lower the current. Components such as bulbs have resistance. When more bulbs are added to a series circuit, resistance increases. This causes the current to decrease. Errors in Red

Bigger picture Topic Potential difference and resistance Component characteristics Current and charge Series Circuits Topic Electric circuits Parallel Circuits

Resistance (Ω) Resistance is what makes it harder for current to flow through a component A higher resistance means less current will flow! Information and 3 new circuit symbols to add to their collection in their books. Students write a description of each component as well. Resistor Variable Resistor Thermistor What do you think the function of each component is?

Resistance SI Unit: Ω E.G R = 100 Ω Symbol: R Measured in: Ohms Key info Resistance Symbol: R Measured in: Ohms SI Unit: Ω E.G R = 100 Ω Key info that students will forget

Resistance in a wire Variables: Independent: Dependent: Control: How does the length of wire affect the resistance? Variables: Independent: Dependent: Control: This is a required practical. Talk the students through the practical and have them come up with dependent independent and control variables. Set power pack voltage to 2v maximum. Power Packs should be switched off between readingsas wire will get hot.

Potential Difference (V) Length of Wire (cm) Potential Difference (V) Current (A) Resistance (Ω) 10 20 30 40 50 60

Resistance = Voltage / Current (in Ω) (in V) (in A) or R = V / I This relationship is known as Ohm’s Law (or V=IxR) V I R Walk through how to use the triangle, also why the equation works. After the students calculate the results in the table for resistance see if they can identify any patterns? You should be able to show that the patterns follow the basics of what happens when you fiddle with the numbers in the equation)

Plot data on a graph! Have students run through what makes a good graph. Plot Length on the X, Resistance on the Y

So what happened? What happened to the resistance? Can you explain it? Remember: Resistance is what makes it harder for current to flow through a component Students should clearly see that as length of wire increased, the resistances also increased. Give a few minutes to discuss findings. Have students think of the long wire as being a traffic jam on a motorway. It takes ages to get to where you're going. The short wire, however, is like a queue at a roundabout - you soon get where you want to be. You can also pupil model this in class with a route to move through and chairs representing particles to collide with. Have students write a conclusion to the experiment explaining what they saw and why. Extension students can write about potential error in the experiement.