# Voltmeters and Ammeters

• Voltmeters and Ammeters are important devices in examining electrical circuits.

• An Ammeter measures electric current in a circuit. The unit of electrical current is the Ampere or “Amp” (A).

• An Ammeter is connected in series within the circuit. This means it is part of the main circuit loop, so all of the current flowing around the circuit also flows through the Ammeter.

• If an Ammeter is connected incorrectly (i.e., in parallel), it could be damaged due to a surge of high current.

• A Voltmeter measures the voltage or potential difference across two points in a circuit. The unit of voltage is the Volt (V).

• Unlike Ammeters, Voltmeters are connected in parallel with the component they are measuring. This means they are connected across the component, providing a separate loop for current to flow.

• If a Voltmeter is connected incorrectly (i.e., in series), it will not record the correct voltage, and could also disrupt the functioning of the entire circuit.

• When reading an Ammeter, it should be noted that current remains the same regardless of where it is measured in a series circuit.

• In contrast, voltage differs across components in a series circuit, so a Voltmeter will show different readings depending on where it is placed.

• Both Ammeters and Voltmeters are designed to have minimal impact on circuit performance. Ammeters have very low resistance, while Voltmeters have very high resistance.

• Ammeters and Voltmeters both contribute to understanding Ohm’s Law, which explains the relationship between voltage (V), current (I), and resistance (R) in an electrical circuit.