How should an ammeter be connected in a circuit?

• A. In parallel
• B. Across a power source
• C. Across a resistor
• D. In series

Answer: (D)

To measure current, the ammeter must be placed in series with the circuit so every electron flowing to the load goes through the meter. An ammeter is designed to have very low resistance, so it doesn’t noticeably affect the current or voltage in the circuit. If you put it in parallel, it would create an alternate path with little resistance, bypassing the load or causing a large current through the meter. Placing it across a power source would effectively short the source, and placing it across a resistor would measure only the current in that branch, not the total circuit current. So the correct connection is in series.