• Go to https://phet.colorado.edu/en/simulation/circuit-construction-kit-dc and click on Download and then Run.
• Drag circuit elements from the carousel on the left into the play area. Connect them together by overlaying the dashed circles. Clicking on the connections allows you to cut them. Delete circuit elements by clicking on them and then selecting the trash can. You are encouraged to play freelyin a simulation you can't hurt anything (neither the equipment nor you!).

Activity 3 | Voltage (Adapted from PhET Colorado²)

Potential difference V, often called voltage, is related to the strength of the force pushing the charges around the circuit. The SI unit of voltage is the volt. The voltage of a battery is determined by its chemistry; typical, non-rechargeable D-, C-, AA-, and AAA-cells are all 1.5 V.

a. Click the reset button in the lower right and set up a one-bulb circuit with two batteries end to end. Then try three batteries end to end. We say these end-to-end batteries are "in series." How is the ammeter reading affected? How is the brightness of the bulb affected?

b. Guess/predict a rule for the voltage of a given set of batteries in series.

c. Verify your predicted rule by putting two batteries in series but make them different voltages (by clicking on at least one of the batteries and changing the value). Drag a Voltmeter from the palate on the right and attach one of the leads to each end the set/group of batteries. Then doubly verify your rule by switching the polarity of one of the batteries.

d. Given your rule, speculate about the internal make-up of a real-life 9-V battery. Examining a 12-V car battery may give you an idea.

e. How does the voltage across the bulb compare to the voltage across the series-combination of batteries?

f. Figure out how to connect two or three batteries "in parallel" (side by side) rather than in series. How do the brightness of and the ammeter readings in the bulb compared to the one-battery circuit?

g. Guess/predict a rule for the voltage of a given set of identical batteries in parallel.