A student builds a circuit containing a battery, a switch, an ammeter, and three identical lamps. She first connects all three lamps in series. She then rebuilds the circuit so that all three lamps are connected in parallel. Describe and explain the differences the student would observe in the brightness of the lamps and the reading on the ammeter when comparing the parallel circuit to the series circuit.

In the series circuit the same current flows through all three lamps, so each lamp receives only one‑third of the battery voltage. The lower voltage gives a lower current through each lamp, making them dimmer.

In the parallel circuit each lamp is connected directly across the battery, so each lamp receives the full supply voltage. The higher voltage causes a higher current through each lamp, so each lamp is brighter.

The ammeter measures the total current drawn from the battery. In the series circuit the current is that of a single lamp, so the reading is low. In the parallel circuit the total current is the sum of the currents through the three lamps, so the ammeter reads a higher value.

Thus lamps are brighter and the ammeter reads higher in the parallel arrangement than in the series arrangement.