Circuits and Components
You need to be able to read circuits and recognise electrical components. I’ve sketched all of the components that you’ll need to know for National 5 at the bottom of this page. You need to know the symbols, function and application of each of these components.
This section should help you get your bearings around electrical circuits, both parallel and series.
Series Circuits
A series circuit is one where the current follows in one path through every component of the circuit.
Current doesn’t vary across a series circuit, and so can be calculated with the first given equation.
Voltage is divided between the components in a series circuit, and so can be calculated with the second given equation.
Total resistance of a series circuit can be calculated, using the third given equation.
Parallel Circuits
Electrical current travels in more than one path in parallel circuits.
Current is divided between the branches of a parallel circuit and can be calculated using the first given equation.
Voltage is equal across each branch of a parallel circuit. The second given equation can be used to calculate voltage in a parallel circuit.
Resistance in a parallel circuit can be calculated with the third given equation.
Transistors
A transistor is a semiconductor that can be used as a switch or to amplify electrical signals and power.
Npn transistors turn on when voltage is greater than or equal to 0.7V.
MOSFET transistors turn on when voltage is created than or equal to 2.0V.
Key Points!
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Series Circuits
Calculate current, voltage and resistance at different points in a series circuit.
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Parallel Circuits
Calculate current, voltage and resistance at different points in a parallel circuit.
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Transistors
A transistor is a semiconductor that can be used as a switch or to amplify electrical signals and power.
Npn transistors turn on when voltage is greater than or equal to 0.7V.
MOSFET transistors turn on when voltage is created than or equal to 2.0V.
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Components
Identify each of these given components and understand their uses.