4-ELC-03

Outcomes

• Pupils can understand how current and voltage are related for bulbs, diodes and wires/resistors
• Pupils can produce the relevant I-V graphs for bulbs, diodes and wires/resistors

Specification References

• 2.11 describe how current varies with voltage in wires, resistors, metal filament lamps and diodes and how this can be investigated experimentally

Main Body of Lesson

Pupils to take experimental current and voltage readings for the following:

• 10 ohm resistor (they have already done this but they need to take the negative values of I and V)
• metal filament bulb
• diode

Once they have finished they need to plot I-V graphs. I suggest getting them to copy down some "ideal" graphs. They need to be able to FULLY explain all of the shapes especially the filament bulb fillament. They also need to be able to talk a little about how the diode acts like a valve (nothing too deep). These are classic exam questions and are generally not tackled well. Try to really reinforce. There is a powerpoint in the folder to (hopefully) help.

Plenary

Use the astounding "Ed's Sig-gen PASCO combo" to demonstrate the I-V characterisics of:

• a 10 ohm resistor
• a 20 ohm resistor (ask them to predict whether the gradient will be steeper or shallower)
• the wires on a standard GCSE resistance of a wire investigation board showing how it produces the same results as a resistor, again you can extend by talking about thickness of the wire
• a bulb
• a diode (works slightly differently but Ed's set-up allows this to be done with ease)

n.b. this can be done at the traditional plenary time OR just after they finish producing their graphs. Up to you.

Additional Information

Resources Required

• PASCO I-V demo board for bulb, diode and resistor
• 1 x board of wires

12 sets of:

• 1 x power supply
• 1 x 10 ohm resistors
• 1 x diodes
• 1 x bulbs
• 1 x simple ammeter
• 1 x simple voltmeter