need help with the second problem. thanks.
Electrostatics Virtual Lab
Content in Black, Procedure in Green, Questions in Blue, Your Answers in Red
Name: _______________________________________________
VIDEOS:
Electrostatics: https://www.khanacademy.org/science/physics/electric-charge-electric-force-and-voltage/charge-electric-force/v/triboelectric-effect-and-charge?modal=1
Coulomb’s Law: https://www.khanacademy.org/science/high-school-physics/electric-charge-and-electric-force/coulombs-law-and-electric-force/v/coulombs-law
Objectives:
Observe what happens to charges at a microscopic level when objects come into contact with other objects in a variety of ways.
Use Coulomb’s Law to calculate the forces between charged particles/objects.
Introduction:
In the universe, there are 4 basic forces:
Gravity
Strong Nuclear
Weak Nuclear
Electromagnetic
The strong and weak nuclear forces act only within the nucleus at very close distances. Gravity acts between two objects that contain mass and can only be an attractive force. The electromagnetic force is a force between two objects that have some charge. The charge value on either object can be either positive or negative. The force between objects with like charges will be repulsive, or they will push each other away. The force between objects with unlike charges will be attractive and will draw each charged object toward the other object. Coulomb described this force and discovered an equation that describes the magnitude of the force:
Just like the equation for the force of gravity between 2 objects, the electric force between objects q1 and q2 requires 2 objects that have some charge on each.
It is possible that if there is no net charge on one of the objects, there can still be a force between it and another object that has some net charge. The uncharged object can be “induced” to have a net charge on part of the object. Charges can move or rearrange themselves so that part of the object is positively charged, and another part can be negatively charged. To determine how this can happen, we must look at the internal molecular or atomic structure of the objects. In the figure below left, both objects have an even distribution of charges. If one of them, say the balloon acquires a negative charge by rubbing it on a sweater, and the balloon is placed next to the brown object, the charges will rearrange themselves to some degree. The overall charge of the brown object is still zero, but the left side of the object will be attracted to the negative charges on the balloon. This is known as creating an “induced” charge in an object.
There are several different ways in which a charge can be “induced” in an object.
The Lab:
Materials:
Chromebook or Computer
Using your access to the internet, you will use several simulations of objects that either have charges on them, or charge is induced in them.
Procedure for Part I:
Open the PhET Simulation “Balloons and Static Electricity” at https://phet.colorado.edu/en/simulations/balloons-and-static-electricity
Make sure the box in the lower left corner has “Show all charges” selected.
Simulation A
Record the electrical state of each of the 3 objects in the simulation (neutral, overly positive, overly negative):
Sweater: Neutral
Balloon: Neutral
Wall: Neutral
Using the mouse, click on the balloon, and holding the mouse down, rub the balloon against the sweater.
Record the electrical state of the 3 objects after the balloon is rubbed against the sweater (neutral, overly positive, overly negative):
Sweater: overly positive
Balloon: overly negative
Wall: Neutral
Let go of the balloon. Record what happens to the balloon. __________________________________________________________________________________________________________________
Simulation B.
Reset the balloon
Bring the balloon close to the wall. Record what happens to the electrical state when the balloon is moved close to the wall
Balloon: Neutral
Wall: Neutral
Simulation C:
Reset the balloon
Rub the balloon against the sweater
Leave the balloon next to the sweater
Record the electrical state of the wall: Neutral
Move the balloon (which should have a net negative charge) close to but not touching the wall. Do not let go of the balloon. Record what happens to the charges in the wall. The negative charges on the wall away from the ballon.
Is the “net” charge on the wall positive, negative, or neutral? Positive
Let go of the balloon. What happens to the balloon? The ballon goes back to the wall.
Part II
In Part II of this lab, you will experience the forces that objects feel when each object has a net charge (either positive or negative).
In the figure above, there are two objects, q1 and q2 (the two spheres). The simulation allows you to alter the charge on each sphere, and whether the charge is negative or positive. The “people” holding the charges in place are applying forces to keep the spheres in place, either pulling on them or pushing them with forces equal and opposite in direction to the force on the sphere due to the electric force on each.
Procedure for Part II:
On your computer, go to the following Phet website: “Coulomb’s Law” at:
https://phet.colorado.edu/sims/html/coulombs-law/latest/coulom HYPERLINK "https://phet.colorado.edu/sims/html/coulombs-law/latest/coulombs-law_en.html"b HYPERLINK "https://phet.colorado.edu/sims/html/coulombs-law/latest/coulombs-law_en.html"s-law_en.html
Make sure the box in the lower right corner has “Force Values” selected.
Using the table below, alter the charges on each sphere according to the values provided, and record the missing variable in the table. Make sure you record the direction of each force. Record the direction in the same box as the force value using ‘right’ or ‘left’.
DataTable
| Trial | q1 (Coulombs) | q2 (Coulombs) | d (meters) | Fq1 (Newtons) | Fq2 (Newtons) |
| 1 | +5.00
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