# Phet charges and fiels | Physics homework help

Complete Part 1 for chapter 18 and part 2 and 3 for chapter 19.

Part 1 What is an equipotential line and how is this simulation related to work and energy?

1)  Go to the PhET simulations.

2)  From the list on the left choose Electricity, Magnets, and Circuits.

3) Now pick “Charges and Fields”.

4)  Turn on “Show Numbers”

5)  Place a positive 1 nano-coulomb charge near the center of the screen.

6)   In the lower left of the screen is a meter for indicating electric potential, in volts,  created by the charge that you introduced. Record the voltage and turn on “Plot”.

7)  This line is much like a line on a geologic topo map. Explain the similarity.

8) You are on the side of a hill with a topo map of the region. If you walked so that your trip follows a topo line you would be doing no work on your backpack. Why?.

9) If a second charge were placed on this line (don’t do it), how much work is need to move it along the line?

10) Move the meter closer to the charge at the center of the screen. What is the new electric potential? Turn on plot again

11)  Remember that electric potential is energy per charge (1 volt = 1 Joule/Coulomb). Is electric potential a vector or a scalar?

12) If a second positive charge were introduced and moved from the first equipotential line created to the second line (closer to the charge), would this involve positive or negative work?

13) Explain.

14) If the second positive charge were moved away from the first Positive charge, would this involve positive or negative work.

15) When energy was studied earlier in the year, a connection was found between kinetic energy, potential energy, positive work, and negative work. What is the connection?

16) Click on “Clear All”

Part 2 What is the relationship between the electric potential at a point in space and the distance from an electric charge?

1)      Place a positive 1 nano-coulomb charge an the screen.

2)      Turn on “Show numbers”

3)      Turn on “tape measure”.

4)      Use the tape measure to find and record the distance from the charge to the equipotential sensor.

5)      Record the voltage as indicated on the equipotential sensor.

6)      Change the location of the positive charge to at least six widely different distances from the equipotental sensor. Record the voltage reading and distance at each location.

7)      Use “Excel” to plot these data sets.

8)      What is the mathematical relation between these variables?

9)      Click on “Clear All”

Part 3 What are the characteristics of the electric field senors?

1) Place a positive 1 nano-coulomb charge  at the center of the screen.

2) Click on “Show Numbers.

3) Bring out an electric field senor.

4) What are electric field units?

5) Is the electric field a scalar or a vector?

6) To do its job, the electric field senor should have a charge.Why?

7) Does the field senor have a positive or negative charge.

8) Turn on the “Tape measure”.

9)  As you sample the electric field further and further from a charged object, you find that the field strength weakens. Do you think the E field vs. distance relation  is an inverse relation, an inverse square, or some other power relation? Use the Electric field sensor and tape measure to collect data sets in order to answer this question. Include the “Excel” graph that you made in order to see if you hypothesis was correct. Were you correct? 