Using a Multimeter to Determine the Direction of Electron Current in a Circuit

A multimeter and a battery are used to show how positive and negative multimeter readings indicate the direction of electron current in a circuit.

Discussion

A digital multimeter can be used to determine the direction in which electrons move in an electrical circuit. Current and voltage readings are positive when electrons move from the negative multimeter jack through the multimeter to the positive multimeter jack.

An AA battery has a + mark on the end that is positively charged and a − mark on the negative end. When the positive end and negative ends of the battery are connected through an electrical circuit, electrons move through the circuit from the negative end of the battery to the positive end.

In this movie the multimeter is set to read DC voltage. When the red (positive) lead is connected to the positive jack of the multimeter and the positive end of the battery, and the black (negative) lead is connected to the negative jack of the multimeter and the negative end of the battery, the meter reading is positive - electrons are moving through the multimeter from the negative jack to the positive jack. When the connections to the battery (but not to the multimeter) are reversed, the reading is negative - the direction of electron flow is reversed.

In the same way, when the multimeter is set to read current, a positive reading means electrons are moving through the multimeter from the negative jack to the positive jack, and a negative reading means electrons are moving in the opposite direction.

In the next movie we will use this information to determine the sign of the charge on an electrophorus.