Electric Charge & Force PhET Simulation Summary

Open the "Balloons and Static Electricity PhET Simulation'.

DO NOT PLAY WITH THE SIMULATION YET.

Click on "Remove Wall" so your simulation looks like the image to the right.

1. Notice there are red and blue circles with symbols inside them that are automatically shown. Hypothesize what these circles represent.

______________________________________________________________

______________________________________________________________

1. Hypothesize (without actually doing it) what will happen if you rub the balloon against the sweater. Why do you predict this?

_______________________________________________________________________________________________________

_______________________________________________________________________________________________________

1. Now, actually click and hold on the balloon to drag it towards the sweater. "Rub" the sweater with the balloon.

List at least 3 observations below:

Observation 1	Observation 2	Observation 3	Extra Observations

1. Hypothesize why the blue particles moved but not the red. HINT: Refer to the anatomy of an atom.

_______________________________________________________________________________________________________

_______________________________________________________________________________________________________

1. After rubbing the balloon on the sweater, pull the balloon all the way to the right and then release it. Describe what happens.

_______________________________________________________________________________________________________

1. Hypothesize why that happened. In other words, what caused the balloon to move?

_______________________________________________________________________________________________________

1. Click on the 'Show charge differences' setting. Describe what you see and hypothesize what you thinkcharge difference means.

_______________________________________________________________________________________________________

1. Net charge refers to the difference in the number of protons and electrons an object has. Based on the charge distribution, objects can have a neutral, positive, or negative net charge. Apply this information to complete the following table.

Object	Net Charge before Rubbing?	Net Charge after Rubbing?	Explain your selections
Sweater	Neutral Positive Negative	Neutral Positive Negative	_____________________________________ _____________________________________ _____________________________________ _____________________________________
Balloon	Neutral Positive Negative	Neutral Positive Negative

When at least one charged object interacts with another object, we see an interaction between the two objects because of anelectrostatic force (electro from electrons andstatic because the electrons are no longer being transferred between objects). This interaction can either be an attraction or repulsion based on the net charge of the interacting objects.

Click on the icon with the yellow and green balloon to add a second balloon, as shown to the right.

Keep the 'Show charge differences' setting.

1. Engage with the simulation and try to find a way to move the yellow balloon using the green balloon. Once you are successful, explain what you did and why it works below:

_______________________________________________________________________________________________________

_______________________________________________________________________________________________________

You should have seen that you can move the balloons when they have the same charge (negative and negative or positive and positive). This works because objects with like charges repel, whereas objects with opposite charges attract.

Reset the simulation by hitting the orange reset icon in the bottom right-hand corner.

Charge the balloon again by rubbing it with the sweater until you collect all of the sweater's electrons.

1. Now bring the balloon near the wall and observe what happens. List at least 3 observations below:

Observation 1	Observation 2	Observation 3	Extra Observations

1. Hypothesize why the charges move the way they do within the wall. What is this phenomenon called?

_______________________________________________________________________________________________________

_______________________________________________________________________________________________________

Now move the balloon just barely off the wall and observe what happens. What happens to make the balloon does something different. In other words, until the balloon moves to a different place, the sweater.

1. Hypothesize why the balloon moved back towards the wall

_______________________________________________________________________________________________________

1. Hypothesize why the balloon moved towards the sweater.

_______________________________________________________________________________________________________

1. How might this be different if you didn't charge the balloon in a way to give it so many electrons?

_______________________________________________________________________________________________________

You should have noticed that once you moved the balloon far enough off the wall, it moved quickly towards the sweater. This is because there was a strong, attractive electrostatic force between the sweater and balloons. Below is a list of variables thatmight affect the size of the electrostatic force. Based on what we've learned so far in this activity, circle which variables/factors you think might affect the electrostatic force between objects.

Mass of Object 1 Net Charge on Object 1 Material of Object 1 Color of Object 1

Mass of Object 2 Net Charge on Object 2 Material of Object 2 Color of Object 2

Distance between Objects 1 & 2 The Universal Electric Constant

1. Explain your selection(s).

_______________________________________________________________________________________________________

_______________________________________________________________________________________________________

The variables that affect the electrostatic force between two objects are:

1) The Universal Electric Constant. 2) Net Charge on Object 1 3) Net Charge on Object 2. 4) Distance between Objects 1 & 2

We will investigate how these variables affect the magnitude of this force by completing another PhET Simulation Summary Investigation. There are a few things to note before we start

• The magnitude of the net charge that an object has depends on how many excess protons or electrons it has.
• The unit of measurement for the charge is a Coulomb [C].
• Both protons and electrons have a charge magnitude of 1.6x10^-19 Coulombs, but they differ in sign (+/-)
• This is a very small amount of charge, which is represented with the symbol "e" (1 e = 1.6x10^-19 C)

Open the "Coulomb's Law PhET Simulation' and select the 'Macro Scale' setting.

*Do not move the charges. Keep the same separation distance of 3 cm between the center of each charge for all trials,

1. Change the charges of the objects by sliding the scale to adjust how many micro-coulombs (10^-6) of charge each object has and record the force magnitude and direction on each charge in the tables below. An example is provided for you.

Object

Charge

Force

Charge

Force

Charge

Force

Charge

Force

Charge

Force

Charge

Force

q1 (Left)

-10 C

-8 C

-6 C

-4 C

319.6 N Right

-2 C

0 C

q2 (Right)

8 C

8 C

8 C

8 C

319.6 N Left

8 C

8 C

Object

Charge

Force

Charge

Force

Charge

Force

Charge

Force

Charge

Force

Charge

Force

q1 (Left)

2 C

4C

6 C

8C

10C

0 C

q2 (Right)

8 C

8 C

8 C

8 C

8 C

0 C

1. What patterns do you notice in the data? List at least 3 observations.

Observation 1	Observation 2	Observation 3	Extra Observations

1. Based on the data and your observations, complete the following sentence frames:

As the magnitude of the charge between interacting objects increases,

the electrostatic force between the objects _______________ (increases or decreases)

at a _________________ (constant, increasing, or decreasing rate).

As a result, the relationship between charge and electrostatic force is: (circle one)

linear inverse horizontal quadratic

Reset the simulation by hitting the orange reset icon in the bottom right-hand corner.

*Do not change the magnitude of the charge on either object. Keep the same charge of -4 C for q1 and 8 C for q2.

1. Change the separation distance between the objects by sliding them closer to or away from each other, adjusting how many centimeters there are between the center of each object. Record the force magnitude and direction on each charge in the tables below. An example is provided for you.

Object	Distance	Force	Distance	Force	Distance	Force	Distance	Force	Distance	Force
q1 (Left) -4 C	10 cm		9 cm		8 cm		7 cm		6 cm
q2 (Right) 8 C

Object	Distance	Force	Distance	Force	Distance	Force	Distance	Force	Distance	Force
q1 (Left) -4 C	5 cm		4 cm		3 cm	319.6 N Right	2 cm		1.4 cm *Smallest Possible Separation
q2 (Right) 8 C			319.6 N Left

1. What patterns do you notice in the data? List at least 3 observations.

Observation 1	Observation 2	Observation 3	Extra Observations

1. Based on the data and your observations, complete the following sentence:

As the separation distance between charged objects increases,

the electrostatic force between the objects _______________ (increases or decreases)

at a _________________ (constant, increasing, or decreasing rate).

As a result, the relationship between separation distance and electrostatic force is: (circle one)

linear inverse horizontal quadratic

Use the word bank below to fill in the blanks appropriately.

Friction Electrostatic Force Polarization Negative Electron Affinity Positive Attract RepeL

You can charge an object through ______________ by rubbing it with another object. The object with a higher ________________

will have more electrons, giving it a net ______________ charge. The object with the lower electron affinity will have a net

______________ charge. If you bring the positively charged object near another positively charged object, they will experience an

electrostatic force and ______________. If you bring the negatively charged object near a neutral object, there will still be an

______________, and the neutral object will undergo ______________ and ______________ the positively charged object.