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# Virtual lab: Series and Parallel circuits

### Learn about electrical circuits with thePhET Circuit construction kit

* Briefly play with the app, learning the drag-and-drop components
* Accurately answer questions in complete sentences, at a high school level.
This must be completed in class to get credit. Unless you have an excused absence, you can’t make up the lab.

### Learning Goals:

Develop a general rule regarding how resistance affects current flow,
when the voltage is constant.
Learn how changing resistance values affect current flow in both series and parallel circuits.

### Series Circuit A

Right click on the resistor, change the value of the resistor and observe what happens to the rate that the electrons move through it. The rate at which the electrons move is called current. Current is measure in Amps

(A) Make a general rule about the relationship between current and resistance.
– 10 points for circuit and accurate answer.

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### Parallel Circuit B

Make observations & draw conclusions. – By right clicking on the resistors, change the values of the resistors, making one very high and one very low and visa versa.
Look for what happens to the current flow through the different resistors.

With regards to circuit B:
(a) Describe current at different locations in the circuit, esp. rate of the current and the value of the resistors.
(b) Explain your observations of the current flow in terms of the water tank model of electricity given to you in class
(c) Describe how your general rule from step 2 relates to your observations
– 20 points for circuit and accurate answer.

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### Circuit C

Change the values of the resistors, making one very high and one very low, and visa versa.
(a) Look for what happens to the current flow through the different resistors.
(b) Describe current at different locations in the circuit.
(c) Explain observations of the current flow in terms of the water-flow analogy.
(d) Describe how your general rule from the beginning relates to your observations.

Water flow analogies for electrical current
– 20 points for circuit and accurate answer.

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### Circuit D: voltage in a series circuit

Build the series circuit shown below. On the left-hand menu, click voltmeter. You can drag-and-drop the red and black leads.

A lead is an electrical connection that comes from some device. Some are used to transfer power; ours are used to probe circuits.

A multimeter is a measuring instrument that combines multiple meters (measuring devices) into one Typical multimeters include

ammeter = measures I (current)
metric unit of current is amperes (A)

ohmmeter = measures r (resistance)
metric unit of resistance is ohms (Ω)
Ω is the Greek letter omega.

voltmeter = measures v (voltage) in a battery,
or the voltage drop across a part of a circuit.
metric unit of voltage is the volt (v).

With the knife-switch closed, what is the voltage drop across:

1. the battery
2. the light bulb
3. the knife-switch
4. the resistor

With the knife-switch open, what is the voltage drop across:

1. the battery
2. the light bulb
3. the knife-switch
4. the resistor

### Circuit E: voltage in a parallel circuit

Build the series circuit shown below. On the left-hand menu, click voltmeter.
You can drag-and-drop the red and black leads.
What is the voltage drop across:

1. the 2 batteries
2. the resistor in the middle
3. the light-bulb
4. Points A and B on the wires.

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### Circuit F: Measuring both I and V

Build the circuit shown here. Use the voltmeter to measure voltage, and the ammeter to measure current. Carefully fill in the 2 data tables. After you have taken the data, answer

(a) Compare the voltage numbers before you changed the resistance, to after you changed the resistance.

(b) Look just at the left column (default values) for current. Compare your numbers, to their locations on the circuit: What’s the relationship between the amount of current in one part of the circuit, to another? (Thinking of the water-flow analogy may be helpful.)

(c) Look at the right column for current. How did changing the value of one resistor affect the circuit (if at all?)

## Learning Standards

Massachusetts 2016 Science and Technology/Engineering (STE) Standards
HS-PS2-9(MA). Evaluate simple series and parallel circuits to predict changes to voltage, current, or resistance when simple changes are made to a circuit.