How to Connect an Ammeter and Voltmeter in a Circuit: Sec 3 Physics Practical Checklist

TL;DR
An ammeter must be wired in series with the component under test; a voltmeter must be wired in parallel across it.
The reason is resistance: an ideal ammeter has zero resistance so it does not steal voltage from the circuit, and an ideal voltmeter has infinite resistance so it does not draw current away from the main loop.
The single biggest misconception at Sec 3 is that current gets "used up" as it travels around a circuit -- it does not. Energy is transferred, but charge is conserved.

This page targets the Sec 3 entry-point angle: how to connect an ammeter and voltmeter in an electric circuit, step by step, with a pre-switch checklist. For the broader O-Level Paper 3 treatment -- rheostat wiring, analogue meter reading, MMO mark criteria, and I-V characteristic experiments -- read the companion post on connecting ammeters and voltmeters in O-Level Physics practicals. For foundational lower-secondary electricity theory, see the IP Combined Science chapter on Electricity and Magnetism Essentials. For all practical experiment guides, visit the O-Level Physics Experiments hub.

1 | Series vs parallel: the two-second recap

Before placing any meter, you need a clear picture of how series and parallel connections differ.

Series connection -- every component is part of a single, unbroken loop. The same current flows through every component in that loop, one after another. If you break the loop at any point, no current flows anywhere in the circuit.

Parallel connection -- the circuit splits into two or more branches that share the same two junction points. Each branch carries its own current, but the voltage across every branch between those two junctions is the same.

This distinction is the key to placing both meters correctly:

• The ammeter must join the series loop because it measures the current that passes through the component.
• The voltmeter must form a parallel branch because it measures the voltage between two points.

A memory hook many students find useful: the letter V forms a shape that spreads across two points, just like a voltmeter spans two terminals in parallel. The ammeter, by contrast, is inserted into the wire -- it is part of the single path, not branching off to the side.

2 | Where the ammeter goes (in series, low resistance)

The placement rule

To measure the current through a resistor, you break the wire at one point and insert the ammeter into that gap. The ammeter becomes part of the series loop. Every coulomb of charge that flows through the resistor must also flow through the ammeter, so the ammeter reads the true current through that component.

Reviewed by

Chee Wei Jie·Academic Advisor (Physics)

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