We Have the Technology

This physics extension module from the Salters’ Science course covers the action of sensors and amplifiers in electronic systems. Potential dividers are studied as a way of supplying different voltages. The action of light dependent resistors and thermistors in potential dividers is studied. Transistors are introduced as devices to give sharp switching in response to changing conditions. Transistors are then considered as amplifiers and some amplifier circuits are investigated. Ideas of memory and feedback are briefly introduced.

Lesson 1: Systems
Students adopt a systems approach to designing circuits which will solve a series of practical problems, for example, sound or light activated warning systems

Lesson 2: Devices and designs
Students build, test and modify one of their systems.

Lesson 3: Divide and rule
Students investigate potential divider circuits. Relationships between resistance and voltage are established.

Lesson 4: Sense and sensitivity
Light or temperature dependent potential dividers, using LDRs or thermistors are built and tested to show how output varies over a range of conditions. Moisture sensors are also discussed.

Lesson 5: Switching over
Students use a transistor with a potential divider to make a sensor circuit that will switch sharply at a given boundary condition.

Lesson 5X: Amplification
Concepts of op-amps are studied, introducing the ideas of gain and this is related to the transistors used with the system.

Lesson 6: In control
Uses of memory and feedback elements are discussed. Effects of positive and negative feedback are shown and students draw flowcharts for a variety of systems.

• URL: http://stem.org.uk/rx5qo