Electric Fields and Forces
Simulation Lab
Name ____________________________________
8th Grade PSI Science
Score: __________/ 40 points
Objective: To understand how electric force affects a given mass.
Materials: Electric Field Hockey Simulation
Procedure:
1) Go to http://phet.colorado.edu/en/simulation/electric-hockey . Then click “Run Now”.
2) Like charges _____________ and unlike charges _____________. The hockey puck
is positive. Drag a positive red charge out of the box in the upper right hand corner.
Move it closer to the hockey puck. Notice the arrow coming from the puck. This
represents the electric force on the puck.
3) What happens to the size of this force, as you bring the charge closer to the puck?
Why does this happen?
4) Position the positive red charge so that it will push the puck into the goal when you
click the start button on the bottom. Click start and observe what happens. As the puck
moves farther from the charge, what happens to the electric force on it? (HINT: You
can hit reset and watch what happens again if you need to.)
www.njctl.org
8th Grade PSI
Types of Interactions
Why does this happen?
5) Why does the puck continue move into the goal, even when the force on it goes down
as it moves away from the charge? (HINT: Recall Newton’s 1st law of motion from the
last unit.)
6) Click “Reset”. Click on the boxes “Field” and “Antialias”. You should see a lot of black
arrows in the field. Describe what these black arrows represent. Why are they darkest
in color close to the positive red charge?
7) Now, start adding more positive red charges directly on top of the red charge that is
already in the field. As you add the red charges, what happens to the black arrows
surrounding them?
www.njctl.org
8th Grade PSI
Types of Interactions
Why does this happen?
8) Click “Reset”. Unclick the “Field” and “Antialias” button. Slide the mass bar at the
bottom all the way to the right so that the puck has a greater mass of 100. Click “Start”
again and watch the puck. How is the motion different compared to when the puck had
a lighter mass? (HINT: Redo the motion with a mass of 25 if you need help recalling
the motion with the lighter mass.)
Explain why.
9) Predict what will happen to the puck if you slide the mass bar down to 1. Write your
prediction below.
Test your prediction using the simulation and describe what happens and why.
www.njctl.org
8th Grade PSI
Types of Interactions
10) Click “reset” and clear the field by clicking on the “clear” button on the bottom. Drag a
negative blue charge from the box. Position the negative blue charge around the puck
to make a goal and press start. Where did you need to place it and why?
Describe what happens to the electric force on the puck as it approaches the goal.
Why does this happen?
Why does the puck keep moving even though as it passes the charge the force on it is
in the other direction?
When the net force on an object is in the same direction as its motion, it
________________.
When the net force on an object is in the opposite direction of its motion, it
______________.
11) Reset and clear the field. Place a positive charge between the puck and the goal at a
height even with the top of the goal. Click the trace button on the bottom so it has a
check mark. Now use two other charges to score a goal. When you have done it, click
“Reset” and raise your hand so the teacher can watch. ___.
www.njctl.org
8th Grade PSI
Types of Interactions
Draw the setup that scored a goal.
Explain the reasoning behind the setup. In other words, how did the arrangement of
negative and positive charges push the puck into the goal?
12) Reset and clear the field. Click Difficulty 1. Use as many charges as you need to in
order to score a goal. Again, when you have done it, click “Reset” and have the
teacher watch. ___.
Draw the setup that scored a goal.
www.njctl.org
8th Grade PSI
Types of Interactions
Explain the reasoning behind the setup. In other words, how did the arrangement of
negative and/or positive charges push the puck into the goal?
13) Reset and clear the field. Now try Difficulty 1 using only two positive charges. Again,
when you have done it, click “Reset” and have the teacher watch. ___.
Draw the setup that scored a goal.
Explain the reasoning behind the setup. In other words, how did the arrangement of
positive charges push the puck into the goal?
www.njctl.org
8th Grade PSI
Types of Interactions
14) Reset and clear the field. Now try Difficulty 2, between the barriers, using no more
than 8 charges (can be less). When you have done it, click “Reset” and have the
teacher watch. ___.
Draw the setup that scored a goal.
Explain the reasoning behind the setup. In other words, how did the arrangement of
positive charges push the puck into the goal?
www.njctl.org
8th Grade PSI
Types of Interactions