NEIEP Mechanics Practice Exam

What is the result of connecting an ammeter directly to the terminals of a power supply or other voltage source?

1. The ammeter will provide accurate readings

2. The power supply will shut down

3. The meter will be damaged

4. The circuit will operate normally

The correct answer is: The meter will be damaged

When an ammeter is connected directly to the terminals of a power supply or any other voltage source, it creates a short circuit. An ammeter is designed to measure current and typically has very low resistance to ensure that it doesn't impede the flow of current in the circuit. However, when placed directly across a voltage source, it allows excessive current to flow through it without any load to limit that current. This excessive current can lead to overheating and ultimately damage the ammeter, as most ammeters are not rated to handle such high levels of current for an extended period. They are intended to be placed in series with a circuit to measure the current flowing through a load, not connected directly across a voltage source. This direct connection results in a dangerous situation for the instrument, often leading to internal component failure and potential destruction of the meter. Therefore, the primary concern when connecting an ammeter improperly is the risk of damaging the device itself due to the unregulated current flow.