Practical Circuit Skills

A-Level Physics requires you to understand not just the theory of circuits but also how to build, measure, and troubleshoot real circuits. This lesson covers the practical skills and measurement techniques you need for both the practical endorsement and the written exams.

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Ammeters and Voltmeters

Ammeters

An ammeter measures current and must be connected in series with the component whose current you want to measure. All the current flows through the ammeter.

An ideal ammeter has zero resistance, so it does not change the current in the circuit. In practice, real ammeters have a small but non-zero resistance. This means connecting an ammeter slightly reduces the current — an effect known as ammeter loading.

For the ammeter reading to be accurate, its resistance must be negligible compared to the rest of the circuit.

Voltmeters

A voltmeter measures potential difference and must be connected in parallel across the component. It measures the difference in electrical potential between two points.