Electric Field Hockey Post-Game Analysis

1. Which direction do electric field lines point for positive charges?

Electric field lines (protons) always point AWAY from positive charges.

1. Which direction do electric field lines point for negative charges? 

Electric field lines (protons) always point TOWARDS positive charges.

1. What do the direction and strength of the field lines indicate for the (positively charged) “puck?” 

The direction and strength of the field lines in this simulation represent where the puck will travel.  For example, since the puck itself is positive, if you put a proton next to it, the puck will travel in the opposite direction because only opposites attract.  The closer the proton is to the puck, the farther the puck will travel.  If a electron is put near the puck, the arrow will point towards the electron because the puck and electrons attract.

1. Did the (positively charged) puck always move in the same direction as the field lines it was passing over? 

No.  If the field lines are all pointing inwards toward a specific electron, then it will have an effect on the puck.  But if the puck is already traveling with a great force (caused by a proton pushing it away) then the puck will make a circular motion around the field lines.  So even though the field lines point downwards, the puck will travel across them (caused by the proton) but eventually end up where the field lines are pointing.

1. What happened (or would happen) if you changed the charge of the puck from positive to negative? 

The puck would react just the opposite as before.  Putting an electron next to the puck would make the puck repel, while putting a proton near the new puck would attract it.

1. What happened when you increased the mass of the puck?
   

As the mass of the puck increases, the acceleration decreases.  This is modeled by the equation: Fnet = mass x acceleration.  So when the mass goes up, the acceleration must go down in order to keep the force the same. 

7. How did the distance between the puck and the particles affect the motion of the puck? 

The closer the puck is to the particles, the greater the attraction.  So when a proton is put very close to the positive puck, then the puck will repel very quickly and with lots of force. On the other hand, if a proton is put far away from the puck, it will only have a weak reaction on the puck and the puck will barely repel.

7. List two or three cool things you got the puck to do. Why did each one happen?
   

1) I could make the puck simple bounce around and into the goal without using any electrons.  I did this by first putting a proton near the puck, then putting a row of protons on top and to the right of the puck, so it would bounce off (be repeled).  Then I had the puck bounce of another row of protons which were lower. Then the puck entered the goal.

2) I could make the puck stand still by simply putting a proton and electron next to the puck.  The electron and proton neutralized each other, and the puck stood still.

9. The field lines on the program are evenly spaced, with darker shades of grey indicating a stronger field. This is a very clear way of presenting this information. However, it is not what we will normally use. Why do you think that is? 

Most of the field lines we use in Physics are hand drawn.  It is difficult to make different shades on paper using a pencil or pen.  It's easier to notice a difference in the strength of the fields by using different lengths of arrows.