Experiments: Intermediate
To complete the GCSE range of activities you will need the following Locktronics equipment (all prices are in pounds sterling and are exclusive of VAT):
| Description | Quantity | Product No |  |
| Baseboard LK750 | 1 | 410-8900 |
| Lead Set LKLS | 1 | 410-8022 |
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| Component carriers: |
| Connecting link | 10 | 410-5250 |
| Switch press | 2 | 410-6207 |
| Buzzer | 1 | 410-6423 |
| Lamp holder | 4 | 410-5291 |
| Lamps | 4 | 410-2347 |
| Diode (1N4001) | 1 | 410-5243 |
| Resistor 1K | 2 | 410-5202 |
| Resistor 100K | 1 | 410-5218 |
| Resistor 10K | 1 | 410-5203 |
| Resistor 180 ohm | 1 | 410-5207 |
| Motor | 1 | 410-4102 |
| Variable resistor 250 ohm | 1 | 410-5208 |
| Variable resistor 10K | 1 | 410-5214 |
| Transistor | 1 | 410-5240 |
| Fuse carrier/universal component carrier | 1 | 410-7936 |
| Reed switch | 1 | 410-5404 |
| Thermistor | 1 | 410-5402 |
| LDR | 1 | 410-5144 |
| Capacitor 10 μF | 1 | 410-5221 |
| Capacitor 2000 μF | 1 | 410-6203 |
| Transformer | 1 | 410-4123 |
| Relay 6V changeover | 1 | 410-7889 |
| NOT gate | 1 | 410-6862 |
| OR gate | 1 | 410-6861 |
| AND gate | 1 | 410-6860 |
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| Other equipment: |
| Cells | 3 |
| Multimeter | 1 |
| Fusewire | 1 |
GCSE SCIENCE CORE:
Calculating Resistance
- Give students a formal definition of resistance.
- Teaches how to calculate resistance from voltage and current measurements before learning how to measure resistance with a DMM.
Characteristics of Electrical Components
- Introduces students to the concept of graphs that characterise a component's behaviour.
- Students then go on to make relevant measurements in order to plot characteristic graphs for a bulb, a resistor, a diode (an LED) and a thermistor.
- Students discuss the significance of the gradients of each graph.
- Tasks can be extended by introducing "reverse bias", comparing the "switch on" voltage of a normal diode to an LED, the negative temperature coefficient of thermistors, and the characteristics of an LDR
Changing Resistance
- Shows that resistance controls voltages and currents in circuits, and that several devices specifically change resistance.
- Students investigate a potentiometer, LDR and thermistor before carrying out a "resistance of a wire" experiment
Energy and Power
- Introduces three equations that link energy and power to measurements of voltage and current in circuits.
- Three example components are used to measure and calculate their energy and power.
Fuse Wire
- Students discuss where fuses are used and how they function.
- Students then carry out two brief experiments with a piece of thin fuse wire (or wire wool strand) which blows under specific circumstances (a short circuit and a current excess).
Transformers
- Students consider how transformers increase (step up) or decrease (step down) voltages - and examples of where this is useful.
- They then experiment with a simple transformer - measuring the voltage and current on both sides.
- Students use the P=VI equation to explain the current pay-off for increasing voltage.
Diodes
- Introduces students to diodes as a "one-way" component.
- Students build diode circuits and experiment with reversing their bias.
- Demonstrates that Light Emitting Diodes also give out light when connected in forward bias.
CIRCUITS – GCSE SCIENCE EXTENSIONS:
Capacitors
- Discusses the structure of capacitors, how they fill up with charge and then can store it.
- Students investigate capacitor charging and the effect of changing the series resistor.
- Students build a circuit where the capacitor is used as a timing device.
Potential Dividers
- Reminds students that components in series share the voltage that is across them.
- Students explore the rules for sharing voltage in potential dividers with simple resistor combinations.
- These rules are then tested and used to explain more complex and variable combinations
Transistor Switching
- Shows the three main parts of a transistor and their functions.
- Explains to students how transistors switch on, and especially that only a small base current is needed to switch them on.
- Students then build two circuits that show transistors in use.
Logic Gates
- Explains to students that micro-electronic circuits use switching components called logic gates that control the functioning of the circuit.
- Students first construct three switching circuits that model AND, OR and NOT behaviour with switches only.
- Next, the three types of logic gates are put into circuits - and truth tables are completed to describe their functioning.
- Finally, two more complicated circuits are built to show how gates can be combined.
Inputs and Outputs
- Introduces the concept that circuits tend to have input and output devices, and some possibilities for each.
- Students start by measuring how the resistance of three input devices change under various conditions.
- Finally, students are encouraged to consider the energy transfers made by several output devices.
Resistance in Series and Parallel
- Resistors can be combined to increase or decrease their overall value.
- Students experiment with series and parallel resistor combinations before writing rules for each type.
- Students are then able to predict the value of any combination which they can then test.
Variable Resistors
- Discusses the potentiometer (variable resistor) with students, and why they have three connections.
- Students then work through a series of four circuits to explore how potentiometers function in different orientations and combinations.
Relays
- Shows that relays are electromagnetic switches where the current in one circuit magnetises a coil that closes a switch in an adjacent circuit.
- Students first build a circuit that shows relay switching.
- The next circuit includes a protective "reverse bias" diode that protects other components in a circuit from the "back emf" produced when a relay switches off.
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