In a circuit with two bulbs, if the switch is operated as described and the circuit is complete, which statement is true about the ammeter placement?

• A. Ammeter in series with the circuit
• B. Ammeter in parallel with the load
• C. Ammeter across the power source
• D. Ammeter across ground

Answer: (A)

Current must be measured by placing the ammeter in the path of the current flow. In a complete circuit, the same current that goes through the load also passes through any series component, so putting the ammeter in series with the circuit lets it carry and measure that same current with minimal disruption (an ideal ammeter has almost zero resistance). If you put the ammeter in parallel with the load, it would provide an alternate path for current, skewing the reading and potentially changing how the bulbs operate. Placing it across the power source would effectively short the source, which is unsafe and does not measure the circuit’s current. Across ground would not give a meaningful measurement of the circuit current.