Fundamentals of Circuits I: Current Models, Batteries & Bulbs

Fundamentals of Circuits I: Current Models, Batteries & Bulbs v 0.1
Investigation 3:
Current and Electric Potential Difference
Since a battery is a device that has an electric potential difference across its terminals, it
is capable of giving energy to charges, which can then flow as a current through a circuit.
Exploring the relationship between the potential differences in a circuit and the currents that
flow in that circuit is an essential part of developing an understanding of electrical circuits.
Since potential differences are measured in volts, a potential difference is informally referred
to as a voltage, and usually denoted by the symbol V . Voltage is an informal term for potential
difference. If you want to talk to physicists, you should refer to potential difference. Communicating
with a sales person at the local Radio Shack store or buying batteries at a hardware
store is another story. There you should probably refer to voltage. We will use these two terms
interchangeably.
You will use voltage probes to measure electric potential difference. The voltage probe has
two clips. When the clips at the ends of the wires are connected at two points in a circuit the
computer can measure the potential difference. Fig. 10 shows our simple circuit from Fig. 5
with a voltage probe connected to measure the voltage across the battery. Note that the word
across describes how the voltage probes are connected.
+
VP1
−
Figure 10: Voltage probe connected to measure potential difference of the battery
Let’s measure the potential difference across different elements of this circuit. You have
available the following equipment.
• Computer with Logger-Pro software
• Lab Pro interface
• D-cell battery and holder
• light bulb and socket
• SPST switch
• two voltage probes
PHYS-204: Physics II Laboratory 13