Volts and Amps: Understanding Current Flow
(Adult Supervision Advised)
- Insulated Wire with Alligator Clips
- 1.5 Volt Battery
- Light Bulb with Holder
- Wire Cutters
Follow these steps:
- Using about 300mm in length of the wires with alligator clips, connect the 1.5 Volt battery, the switch and the low voltage light bulb in series.
- Place the positive probe of the Voltmeter on the top (positive terminal) of the battery and place the negative probe of the Voltmeter to the bottom (negative terminal) of the battery. (Note: A Voltmeter measures the difference in potential across both terminals of the battery. The meter is connected ‘in parallel’ and will read 1.5 Volts, whether the lamp switch is turned on or off.)
- The Milliammeter needs to be connected ‘in series’ – which implies it should be connected directly in the path of the current flow. The Milliammeter measures how much current is flowing through the circuit.
- Once this is setup, you should notice that when the switch is open, the bulb is drawing power, also called ‘current’, so that the light can shine. This ‘power’ is measured by the Milliammeter, while the potential of the battery is measured by the Voltmeter.
WHAT WE HAVE LEARNED:
In this experiment, the path of the current is ‘opened’ by turning on the switch. This allows the current to flow from the switch through the battery and the bulb, then back to the switch. This can also be stated as the current is flowing in a ‘loop in series’. This current flow is measured by the milliammeter and needs to be connected directly within the flow or ‘in series’. The Voltmeter measures the difference in potential across two terminals of a battery and needs to be connected ‘in parallel’. When the switch is closed, the path and the Voltmeter will still show a ‘potential’, however the milliammeter will drop to zero.
TERMS TO UNDERSTAND:
Milliammeter: A sensitive ammeter for detecting small currents, graduated in milliampereres, or amps.
Voltmeter: An instrument for measuring electrical potential in volts.
In Parallel: Connected at the same time. Electrical components connected sided by side, instead of in series.
In Series: Connected one after another. Electrical components connected in a chain, instead of in parallel.