How to Tell the Direction of a Circuit
- 1). Check that you have a complete operational circuit. For example, there needs to be a wire connected to the positive battery terminal and the opposite end connected to an electrical item; a flashlight bulb works well as it lights up when connected. There must also be another wire attached to the other terminal on the electrical item and the opposite end connected to the negative battery terminal. This forms a complete circuit.
- 2). Turn on your multimeter and then set the dial to read amperes (Ah), or insert the plug on the end of the red multimeter cable into the ampere socket on the front of the meter. Adjust the setting using the dial so it reads milliamp hours (mAh). Batteries only produce a small current so measuring mAh gives a more accurate reading.
- 3). Put the bare metal pole on the end of the red wire from the meter onto the terminal on the electrical unit that has a wire that is also connected to the positive terminal on the battery. Put the metal pole on the end of the black wire from the meter onto the other terminal on the electrical item. This is the terminal that has a wire connected to the negative battery terminal.
- 4). Read the meter. It measures the mAh flowing in the circuit. This tells you that the direction of the current in the circuit is flowing from the positive terminal on the battery, through the electrical item and returning to the negative battery terminal.
- 5). Put the red metal pole from the meter onto the negative battery terminal and leave the black pole on the same terminal on the electrical item, you find the meter reading drops to zero. This is because you have reversed the polarity and the meter can't determine a current.