Lab 2: Charges and Fields
Name:
1. Play with the simulation (Charges and Fields: https://phet.colorado.edu/en/simulation/charges-and-fields) and
get oriented with all of the different options. This should help you understand the lab better.
Activity 1
2. From the box at the bottom of the screen, drag a red +1 nC charge into the middle of the screen.
3. If not already selected: Select ‘Electric Field’. How does the brightness of the arrow relate to the strength of
the field? What happens when you check/uncheck ‘Direction only’? Which way do the arrows point for a
positive charge?
The brightness of the arrow reflect the strength of the electric field. The brighter they are, the stronger the field.
When you check/uncheck the “Direction Only”, it removes the arrow brightness and shows the direction of the field.
The arrows point outward, indicating that the electric field moves away from the charge.
4. Drag the red +1 nC charge back into the box at the bottom, and then drag a blue –1 nC charge onto the
screen. Which way do the electric field arrows point for a negative charge?
The arrows point inward towards the negative charge which means the field lines end on negative charges.
5. Click on the yellow Sensor at the bottom and drag it across the electric field. What information do the
Sensors show?
The sensor shows the electric field strength and also the direction when you move it across different
points/locations.
6. What happens to the electric field as you move further from the charges?
The electric field strength decreases as the distance is greater from the charges.
7. Take the Voltage meter (labeled ‘0.0 V’). What information does the voltmeter give? What information is given
when you click on the pencil (you should have a green circle)? What does the green circle represent? (If you’re
not sure, move on and come back to this later.)
The voltmeter measures electric potential at different points throughout. When you click the pencil it allows you to draw
equipotential lines. The green circle represents a point of equal potential.
Activity 2
(If you want to reset the screen, click on the orange circle arrow in the bottom right corner. Do this before each activity)
8. How can you make a charge of +2q? How can you make a charge of -3q?
You can make a charge of +2q by dragging 2 of the +1nc charges and putting them in the same place. You can make
a charge of -3q by putting 3 -1nc charges in the same place.
9. Determine what charges (magnitude and positive/negative) would give you the electric field lines shown below?
, (You may need to try different combinations to determine the magnitudes of each charge.)
You can make a Dipole Field by placing one positive charge and one negative charge that have the same magnitudes. You can create
unequal charges by having one charge larger than the other which leads to asymmetric field lines. You would give +2nc of the
+vc charge and -1 nc of the -vc charge to show the scheme above in the figure.
10. When you have two opposite but equal magnitude charges along a horizontal line (similar to the picture
above), where is the electric field the greatest? Is there ever a point where the field will be zero?
When you have two opposite but equal magnitude charges along a horizontal line, the electric field is the greatest
between the charges. Yes, it will be zero at a point outside of the charges along the axis.
11. When you have two of the same charges along a horizontal line, where is the electric field the greatest? Is there
ever a point where the field will be zero?
When there are two of the same charges (negative or positive) along a horizontal line, the electric field is the
greatest close to the charges. There is a zero field region between the charges called a neutral point.
12. Determine what charge/charges (magnitude and positive/negative) would give each the lines of
equipotential shown below?
(For each situation, turn the ‘Electric Field’ on and off to see how the electric field lines compare to the equipotential lines)
a) b)
Name:
1. Play with the simulation (Charges and Fields: https://phet.colorado.edu/en/simulation/charges-and-fields) and
get oriented with all of the different options. This should help you understand the lab better.
Activity 1
2. From the box at the bottom of the screen, drag a red +1 nC charge into the middle of the screen.
3. If not already selected: Select ‘Electric Field’. How does the brightness of the arrow relate to the strength of
the field? What happens when you check/uncheck ‘Direction only’? Which way do the arrows point for a
positive charge?
The brightness of the arrow reflect the strength of the electric field. The brighter they are, the stronger the field.
When you check/uncheck the “Direction Only”, it removes the arrow brightness and shows the direction of the field.
The arrows point outward, indicating that the electric field moves away from the charge.
4. Drag the red +1 nC charge back into the box at the bottom, and then drag a blue –1 nC charge onto the
screen. Which way do the electric field arrows point for a negative charge?
The arrows point inward towards the negative charge which means the field lines end on negative charges.
5. Click on the yellow Sensor at the bottom and drag it across the electric field. What information do the
Sensors show?
The sensor shows the electric field strength and also the direction when you move it across different
points/locations.
6. What happens to the electric field as you move further from the charges?
The electric field strength decreases as the distance is greater from the charges.
7. Take the Voltage meter (labeled ‘0.0 V’). What information does the voltmeter give? What information is given
when you click on the pencil (you should have a green circle)? What does the green circle represent? (If you’re
not sure, move on and come back to this later.)
The voltmeter measures electric potential at different points throughout. When you click the pencil it allows you to draw
equipotential lines. The green circle represents a point of equal potential.
Activity 2
(If you want to reset the screen, click on the orange circle arrow in the bottom right corner. Do this before each activity)
8. How can you make a charge of +2q? How can you make a charge of -3q?
You can make a charge of +2q by dragging 2 of the +1nc charges and putting them in the same place. You can make
a charge of -3q by putting 3 -1nc charges in the same place.
9. Determine what charges (magnitude and positive/negative) would give you the electric field lines shown below?
, (You may need to try different combinations to determine the magnitudes of each charge.)
You can make a Dipole Field by placing one positive charge and one negative charge that have the same magnitudes. You can create
unequal charges by having one charge larger than the other which leads to asymmetric field lines. You would give +2nc of the
+vc charge and -1 nc of the -vc charge to show the scheme above in the figure.
10. When you have two opposite but equal magnitude charges along a horizontal line (similar to the picture
above), where is the electric field the greatest? Is there ever a point where the field will be zero?
When you have two opposite but equal magnitude charges along a horizontal line, the electric field is the greatest
between the charges. Yes, it will be zero at a point outside of the charges along the axis.
11. When you have two of the same charges along a horizontal line, where is the electric field the greatest? Is there
ever a point where the field will be zero?
When there are two of the same charges (negative or positive) along a horizontal line, the electric field is the
greatest close to the charges. There is a zero field region between the charges called a neutral point.
12. Determine what charge/charges (magnitude and positive/negative) would give each the lines of
equipotential shown below?
(For each situation, turn the ‘Electric Field’ on and off to see how the electric field lines compare to the equipotential lines)
a) b)
