Unit 4 Week 4 Lab Electric Circuits Students 1

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Feb 20, 2024

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Unit 4 Lab 1 Unit 4 Lab 1 Supplemental Lab: Electric Circuits Name 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). A link to this simulation is on the bottom: https://phet.colorado.edu/sims/html/circuit-construction-kit-dc/latest/circuit-construction-kit- dc_en.html After opening the lab, create the following circuit: Student Voltage Resistor - Electric bulb Student name 15 V 5 Ω Once the circuit is conducting current, make sure the simulation is set to show electrons. In what direction is the electron current flowing in the circuit? a From the negative terminal (black end) through the resistor ending at the positive terminal (copper end) b From the positive terminal (copper end) through the resistor ending at the negative terminal (black end) c The current alternates between one direction and the other. Put an X in the yellow box to the left of your choice. 1

Unit 4 Lab 1 Change the setting so it shows conventional current. Now which way does the current flow? a From the negative terminal (black end) through the resistor ending at the positive terminal (copper end) b From the positive terminal (copper end) through the resistor ending at the negative terminal (black end) c The current alternates between one direction and the other. Substitute the voltage (V) and the resistance (R) into Ohm’s Law to demonstrate the current reading is correct. Your simulation readings should confirm this. value Unit (V, Ω, or A) Current = I = V R = ¿ Now double the voltage. Write the new voltage here Component Quantity Value Unit (V, Ω, or A) Battery Voltage Resistor (light bulb) Resistan ce Record the reading on your current meter: Current So when the voltage is doubled, the current is 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. Record your values. Component Quantity Value Unit (V, Ω, or A) Battery Voltage Resistor (light bulb) Resistan ce Record the reading on your current meter: Current So when the resistance is doubled, the current is a ½ of what it was. b ¼ of what it was. c 4 times what it was d 2 times what it was. 2

Unit 4 Lab 1 Keep the voltage and Resistance the same and calculate the power of the current. Calculation Value Unit Power = VI =() × ()= ¿ Cut the resistance of the light bulb in half and recalculate power. Component Quantity Value Unit (V, Ω, or A) Battery Voltage Resistor (light bulb) Resistan ce Record the reading on your current meter: Current Calculation Value Unit Power = VI = ( 30 ) × ( 6 ) = ¿ 180 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: Adding Resisters in Series For this part, reset the circuit to how it was at the start of Part 1 . Component Quantity Value Unit (V, Ω, or A) Battery Voltage Resistor (light bulb) Resistan ce Record the reading on your current meter: Current Break the circuit between the resistor and the ammeter (bottom right) and insert a light bulb so the current flows through the first light bulb and then the second and then the ammeter. Change the resistance of the new bulb to equal the first bulb. 3

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Unit 4 Lab 1 Component Quantity Value Unit (V, Ω, or A) Battery Voltage 2 resistors in series, with the same resistance Record the reading on your current meter: Current What has happened to the current in the circuit? a It is half of what it was. b It is ¼ of what it was. c It is 2 times what it was. d It is 4 times what it was. Use Ohm’s Law for calculating resistance to calculate the total resistance of the circuit. value Unit (V, Ω, or A) Resistance = R = V I = ¿ Double the second light bulb’s resistance (R2) and record the two resistance values below. Component Quantity Value Unit (V, Ω, or A) Battery Voltage Resistor 1 (top) = R 1 R 1 Resistor 2 (bottom) = R 2 R 2 Record the reading on your current meter: Current Click and drag the voltmeter from the right onto the simulation. Place the red probe between the top resistor and the positive (copper) terminal of the battery. 4 R1, same resistance as in Part 1

Unit 4 Lab 1 Place the black probe on the other side of the top resistor. See diagram for how this should look (except your voltage reading will be different). Record the voltage across Resistor 1 (top). Call this V 1 . Record it below. Move the probes down to read the voltage across the bottom resistor. Call this V 2 . Value Unit (V, Ω, or A) Voltagedrop across R 1 = V 1 = ¿ Voltagedrop across R 2 = V 2 = ¿ Total Drop across both resistors = This total should be the same as your battery voltage. Part 3: Adding Resistors in Parallel Return the simulation to the way it was at the start of Part 1, using the same values as were specified on the first page of the lab. Component Quantity Value Unit (V, Ω, or A) Battery Voltage Resistor (light bulb) Resistan ce Record the reading on your current meter: Current Now add a resistor in parallel, setting the second light bulb’s resistance equal to the first . Add a switch between the two resistors as shown below. Your circuit should look like this: 5 If your voltage reads a negative number, reverse the black and red probe positions.

Unit 4 Lab 1 Value Unit (V, Ω, or A) Current with switch open Current with switch closed When the switch is closed, the first light bulb a gets dimmer b gets brighter c stays the same brightness Add an Ammeter to each leg of the parallel circuit to measure the current through each light bulb. The circuit should look something like this: 6

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Unit 4 Lab 1 Record the current through the first (left) resistor. Call this I 1 . Record the current through the second resistor with the switch closed. Call this I 2 . Record the total current going back to the battery. Call this I total . Value Unit (V, Ω, or A) Current throughR 1 = I 1 = ¿ Current throughR 2 = I 2 = ¿ Total current going back to battery I total should equal I 1 + I 2 Open and close the switch so the right light bulb goes out and comes back on again. What happens to the current through the left light bulb (I 1 )? a It stays the same. b It doubles. c It is cut in half. Calculate the total Resistance of the two resisters in parallel. value Unit (V, Ω, or A) Resistance = R = V I = ¿ Conclusions: Adding resistors in parallel causes the total resistance of the circuit to a go up. b stay the same c go down 7

Unit 4 Lab 1 Adding resistors in parallel causes the current coming out of the battery to a go up. b stay the same c go down As resistors are added in parallel the current through a resistor already carrying current a goes up. b stay the same c goes down As light bulbs are added in parallel, the bulbs already carrying current a get brighter b stay the same brightness c get dimmer 8