Circuits Gizmo Worksheeet PDF

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physics gizmo worksheet...

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Name: Christian

Date: 7/20/21

Student Exploration: Circuits Vocabulary: ammeter, circuit, current, electron, ohmmeter, Ohm’s law, parallel circuit, resistance, resistor, series circuit, voltage Prior Knowledge Questions (Do these BEFORE using the Gizmo.) Strings of holiday lights can be designed in one of two ways. In some strings of lights, each light is connected to the others along a single wire (in series). In others, each light is attached to its own wire (in parallel). 1. Suppose a single light bulb burns out. How do you think this will affect lights that are strung along a single wire? (

/1 KU) If single bulb burns out, all lights will switch off

2. How will a single burned-out bulb affect the string of lights if each light is attached to its own wire? (

/1 KU) If single bulb burns out then it will not affect the string of lights, provided

each light is attached to its own wire

Gizmo Warm-up The Circuits Gizmo™ shows a circuit board and a variety of components. Create a circuit with a battery, a light switch, a wire, and a light bulb, as shown. (Click the light switch to turn it to OFF.) 1. Click the light switch to turn it to ON. What happens? If the switch is turn ON, the light bulb will also turn on 2. Turn on Show current and select Electron flow. The moving dots represent a current of electrons—tiny, negatively charged particles—moving through the wire. Voltage is a measure of how much more potential energy an electron at one end of a battery has than an electron at the other end of the battery. ***Add an ammeter to the circuit**** A. How does changing the battery’s voltage (click on the battery and move the slider to adjust the voltage) affect the current? ( /1 KU) Changing battery voltage will change current B. How does changing the battery’s voltage affect the brightness of the light? (

/1 KU)

Changing battery voltage will also change brightness of light Changing battery voltage will also change brightness of light Changing battery voltage will also change brightness of light Changing battery voltage will also change brightness of light Changing battery voltage will also change brightness of light

Changing battery voltage will also change brightness of light Changing battery voltage will also change brightness of light Changing battery voltage will also change brightness of light Changing battery voltage will also change brightness of light Changing battery voltage will also change brightness of light

Changing battery voltage will also change brightness of light Changing battery voltage will also change brightness of light C. Remove a wire. (Click and drag the wire off) What happens? ( Removing the wire turns the light bulb off

/1 KU)

Get the Gizmo ready: Activity A:

 Click Clear. Create the circuit shown at right. (Use the 10-ohm resistor.)  Click on the battery. Set the Selected battery voltage to 10 volts.

Ohm’s law

Introduction: Resistors are devices that slow the flow of current in a wire. The resistance of the circuit to current is measured in units called ohms (). Question: What is the relationship between voltage, current, and resistance? 1. Form hypothesis: How do you think increasing the resistance in a circuit will affect the current in the wire? (

/1 KU) The Hypothesis can be formed that increasing resistance

will decrease current 2. Observe: Turn the light switch On to start the flow of current. An ammeter is a device that measures current in Amperes (A). Drag the Ammeter ( ) to various parts of the circuit. A. Is the current the same throughout, or does it change? ( /1 KU) the current is same throughout B. What is the current in the wire now? ( /1 KU) 2.7 amps

3. Collect data: Measure the current in the circuit using the resistor and voltage combinations given below. Voltage

Resistance

Current

10 volts

10 ohms

1A

20 volts

10 ohms

2A

30 volts

10 ohms

3A

Voltage

Resistance

Current

50 volts

20 ohms

2.5A

50 volts

100 ohms

0.5A

50 volts

200 ohms

0.25A

4. Analyze: What is the mathematical relationship between voltage ( V), resistance (R), and current (I)? Express your answer as an equation: (

/1 KU) V=IxR

This equation is known as Ohm’s law. 5.

Test your equation with other combinations of voltage and resistance. Modify the equation if necessary.

I= V/R R= V/I 6. Apply: Use Ohm’s law to find the resistance of the light bulb in the Gizmo. What is it? Calculations: ( /1 TI) R=V/I R= 20V/1.33A R= 15 omhs Get the Gizmo ready: Activity B: Series circuits

 Click Clear.  Create a circuit as shown.  Click the battery to select it. Set the Selected battery voltage to 10 volts.

Question: In a series circuit, there is only one path for charge to flow. What are the properties of series circuits? 1. Observe: Turn the light switch ON and observe the light bulb. Then start replacing the wire segments with new light bulbs. A. How does each new light bulb affect the others? (

/1 KU) they take up electricity

B. Use the Ammeter to measure the current in various parts of the circuit. Is the current the same throughout, or does it change? (

/1 KU) the current is the same

throughout

2. Form hypothesis: How do you think the total resistance of a series circuit is calculated? (

/1 KU) The sum of the resistor values

3. Experiment: Create a series circuit with a 10-volt battery and four 10-ohm resistors, as shown. Measure the current. A. Based on the voltage and current, what is the resistance of the circuit? (Hint: Use Ohm’s law.) 40 ohms Calculations: (

/1 KU)

R=V/I R=10V/0.25a R=40 ohms

B. Ohmmeters measure resistance. Remove the battery and attach the terminals of the Ohmmeter ( ) to the ends of the circuit, where the battery used to be attached. What is the resistance? 40 ohms 4. Make a rule: How do you calculate the total resistance of a series circuit? (

/1 KU)

You can find the total resistance of a series circuit from the sum of the resistor’s values Extend your thinking: Replace the battery. Turn on Show current and remove one resistor. Why would it be a problem if your household appliances were connected in a series circuit? ( /1 TI) It would be inefficient as all the appliances may not need the same voltage to work efficiently. Get the Gizmo ready: Activity C: Parallel circuits

 Click Clear.  Create a circuit as shown.  Click the battery to select it. Set the Selected battery voltage to 15 volts.

Question: In a parallel circuit, there is more than one path along which charges can flow. What are the properties of parallel circuits? 1. Observe: Turn the light switch ON and observe the light bulb. Then add two more light bulbs to the circuit, parallel to the first two. A. How does each new light bulb affect the others? ( same

/1 KU) the rest still work the

B. Use the Ammeter to measure the current in various parts of the circuit. Is the current the same throughout, or does it change? Explain: (

/1 KU) The current varies in

the circuit depending on the resistor. 2. Form hypothesis: How do you think the total resistance of a parallel circuit is calculated? ( /1 KU) by finding the sum of the currents through each path is equal to the total current that flows from the source. 3. Experiment: With the battery voltage set to 15 volts, measure the current in a parallel circuit with 1, 2, 3, and 4 light bulbs. (In each case, place the ammeter next to the battery.) Use Ohm’s law to calculate the total resistance of the circuit. Record results below. Number of light bulbs

1

2

3

4

Voltage

15 volts

15 volts

15 volts

15 volts

Current

2 amp

4 amps

10 amps

8 amps

0.03 ohms

0.04 ohms ( /1 TI)

Total resistance 0.01 ohms 0.02 ohms Show one calculation for the table above: (not all 4)

4. Make a rule: How would you find the resistance of a parallel circuit with n identical resistors? ( /1 TI) The Resistance of N Resistors in Parallel is used to calculate the resistance of N identical resistors in parallel. RN=(NR)−1 R N= (NR) − 1 5. Apply: What will be the total resistance and current in a parallel circuit with a 15-volt battery and three 10-ohm resistors? Test your answers with the Gizmo (Show calculations) (

/2 TI) R=10+10+10=30

Total resistance: 0.03 ohms

1 30

= 0.03 ohms Current: 10 amps

Activity C (continued from previous page) 6.

Extend your thinking: Household appliances are usually connected in a parallel circuit. Why do you think it might be a problem if too many appliances are turned on at once? (Hint: current in a wire also produces heat.) ( /1 TI)

A powerpoint overload occurs when you exceed the maximum amperage of the electrical circuit you are using. This can be caused by plugging too many appliances into the one powerpoint or running appliances that draw high amps at the same time. The result of an overload can be a short circuit and quite possibly a fire.

7. Calculate: Determining the total resistance of a parallel circuit when there is a variety of resistors is more complex. 

The total current in the circuit (I) is equal to the sum of currents in each branch:



Ohm’s law (V = IR) can be rewritten as I = V / R. Substituting this expression into the equation above:



(Note: Since each branch of the circuit might have a different resistance, we write R1, R2, and so forth. But the voltage is the same across each branch, so V is used for each term.)



Divide each side of the equation by V, and you get an expression for the total resistance of the circuit:

8. Practice: Determine the total resistance of each of the following parallel circuits. (

/5 TI)

A. A parallel circuit with a 20-ohm resistor and a 10-ohm resistor. 6.67 B. A parallel circuit with two 20-ohm resistors and a 10-ohm resistor. 5.0 C. A parallel circuit with a 15-ohm light bulb and a 20-ohm resistor. 8.57 D. A parallel circuit with two 100-ohm resistors and a 20-ohm resistor. 14.3 E. A parallel circuit with a 10-ohm, 20-ohm, 100-ohm and 200-ohm resistor. 6.1

Activity D: Solving complex circuits

Get the Gizmo ready:  Click Clear to remove all components from the CIRCUIT BOARD.

Introduction: Solving a complex circuit may look difficult, but all you have to do is be patient and solve one part of the circuit at a time. Use these two rules to find the resistance of a part of a circuit: 

For components connected in series, the equivalent resistance is the sum of the resistance of each component: Rt = R1 + R2 + … + Rn.



For resistors connected in parallel, use the equivalent resistance equation:

1 R Total

=

1 1 1 1 + + + .. .+ Rn R1 R 2 R 3

Goal: Determine the resistance and current in a circuit with parallel and series elements. 1. Calculate: Use the Gizmo to create the circuit shown at below. Next, find the equivalent resistance of the outlined parallel component of the circuit. Show your work. (Hint: The lowest common denominator of the three fractions is 60.)

Table 1

Load 10 series 10 parallel 20 parallel Bulbparallel Bulbseries Total

V 2.22V 1.56V 1.56V 1.56V 3.33V 10 V

I

R 10  10  20  15  15 

Calculation of Rp:

(

/1 TI)

1/R = 1/15 + 1/20 + 1/10 1/R = 13/60 R = 60/13 R = 4.6 ohm

Equivalent resistance of parallel component: 4.6 ohms

2. Interpret: Now that you found the resistance of the parallel part of the circuit, what do you think you will do next? (

/1 TI) find the resistance of the series circuit

Load 10 series

V

I

R 10 

Rp Rp

Bulbs Total Table 2

15  V

3. Calculate: Add up the resistance of each part of the circuit to find the equivalent resistance of the whole circuit. What do you get? Calculation of Rs or RT:

29.6 ohms (

/1 TI)

4. Check: Remove the battery from the circuit. Connect the two parts of the Ohmmeter to the ends of the circuit, where the battery was attached. What is the resistance? 29.6 ohms (Activity D continued on next page)

Activity D (continued from previous page) 5. Apply: Remove the ohmmeter and reattach the battery. Set the Selected battery voltage to 10 volts. What do you expect the total current to be through this circuit? ________________ Calculation of IT:

(

/1 TI)

Check your answer by placing the Ammeter on the circuit near the battery.

6. Analyze: The following questions can be answered by completing the tables of the previous two pages of Activity D as a guide: You can use Ohm’s law (I=V/R) to calculate the current and voltage through each component of the circuit. Recall that the current is the same through each series component but gets split up in the parallel section of the circuit. (Kirchhoff’s Laws) Show your calculations in the spaces below: Table 2 Data: A. What is the voltage across the10-ohm resistor in series? _____________________ Calculations: ( /1 TI)

B. What is the voltage across the last 15-ohm light bulb? ________________________ Calculations: ( /1 TI) C. What is the voltage across the middle, parallel section of the circuit? _____________ Calculations: ( /1 TI)

Transfer this voltage to the 3 loads in Table 1: (KVL parallel circuits) D. What is the current in each branch of the parallel section? Light bulb: _____ 20-ohm resistor: _____ 10-ohm resistor: _____ Calculations: ( /3 TI)

E. How does the sum of the currents through the parallel loads compare to the current in the rest of the circuit: (Very close or Very different) (. /1 TI)

KU

TI

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TOTAL

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