Physics

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4.3Orginal.docx

Name: __________________________________ Date: ____________________

Below is the tool for the assignment:

Unit 4 Circuits and Ohm’s Law using the software below. You will complete this lab and at the bottom include a screen shot of your set-up.

This lab requires each student create his or her own simulated circuits using the PhET Circuit Construction Kit Virtual Lab (be sure you use the HTML5 version, not the Java version). https://phet.colorado.edu/sims/html/circuit-construction-kit-dc-virtual-lab/latest/circuit-construction-kit-dc-virtual-lab_en.html

After opening the lab, create the following circuit:

Part 1: Ohm’s Law

The simulation shows electrons flowing from the negative terminal of the battery (black end), through the resistor (light bulb) and the positive terminal (copper colored end). Change the current direction by selecting “Conventional Current.” This shows the direction physicists thought current was flowing before the existence of the electron was discovered.

Set the initial voltage and resistance using letters from your first and last name as follows:

First letter of first name

Voltage

First letter of last name

Resistance

A-C

5 V

A-C

5 Ω

D-F

6 V

D-F

6 Ω

G-I

7 V

G-I

7 Ω

J-L

8 V

J-L

8 Ω

M-O

9 V

M-O

9 Ω

P-R

10 V

P-R

10 Ω

S-U

11 V

S-U

11 Ω

V-Z

12 V

V-Z

12 Ω

Change the setting on the battery and light bulb by clicking on the component and using the arrows and/or slider at the bottom of the simulation screen.

Note: in all answers in this lab, the answer is not correct unless it contains both the correct number and the correct unit.

Enter the values you are using in the table below. Include units with all numbers.

Voltage

Resistance

Current

Substitute the voltage (V) and the resistance (R) into Ohm’s Law to demonstrate the current reading is correct.

Result of this calculation =

Now double the voltage. Indicate in the following table the values of the circuit after making the change.

Voltage

Resistance

Current

So when the voltage is doubled, the current is (put an X next to your choice)

a

½ of what it was.

b

¼ of what it was.

c

4 times what it was.

d

2 times what it was.

Do not change the voltage of the battery from new value (listed above). Double the resistance.

Indicate in the following table the values of the circuit after making the change.

Voltage

Resistance

Current

So when the resistance is doubled, the current is (put an X next to your choice)

a

½ of what it was.

b

¼ of what it was.

c

4 times what it was.

d

2 times what it was.

Keep the voltage and Resistance the same and calculate the power of the current.

Formula

Substituted values from your circuit

Result

Increase the resistance of the light bulb by 5 Ω.

Indicate in the following table the values of the circuit after making the change.

Voltage

Resistance

Current

Formula

Substituted values from your circuit

Result

The simulation indicates the relative brightness of the light bulb by the length of the rays around the bulb.

The lower resistance light bulb ___________ than the bulb with the higher resistance.

a

was brighter

b

was the same brightness

c

was dimmer

Part 2: Resistors in Series

When current flows through two resistors as in this circuit, the resistors are said to be connected In Series .

Set up the circuit pictured above. Then change the battery voltage to the value used at the start of part 1 and change the resistance of both light bulbs to the value used at the start of part 1.

With the switch closed (so current flows through it), the current should be the same as it was at the beginning of part 1.

What happens when you close the switch?

Record the voltage and current of your circuit.

Voltage

Current

Use Ohm’s Law to calculate the effective resistance of the combination of two resistors in series.

Formula (provide the formula you used)

Result (Resistance of 2 resisters in series)

Resistance of each individual light bulb

When the switch is closed and current flowed through both bulbs, first light bulb

a

becomes brighter.

b

stays the same brightness as it was.

c

becomes dimmer.

Part 3: Resistors in Parallel

When current flows through two resistors as in this circuit, the resistors are said to be connected In Parallel .

As in Part 2, change the voltage of the battery and the resistance of each resistor to the values used at the beginning of part 1. Indicate your values below with the switch open (no current flowing through the switch). With the switch open (so no current flows through the switch), the current from the battery should be the same as at the start of part 1.

With the switch open, indicate the values of each current meter.

Meter

Current

Current coming out of the battery

Current through left light bulb

Current through right light bulb

Close the switch (so current flows through it) and indicate the currents again.

Meter

Current

Current coming out of the battery

Current through left light bulb

Current through right light bulb

When the switch is closed and current flowed through both bulbs, right light bulb

a

becomes brighter.

b

stays the same brightness as it was.

c

becomes dimmer.

Use Ohm’s Law to calculate the effective resistance of two resistors in parallel.

Formula (provide the formula you used)

Result (Resistance of 2 resisters in parallel)

Resistance of each individual light bulb

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