SCN3797-ABED_1: 10.1 Non Uniform Electric Fields

Lab: Storing Energy in Non-Uniform Electric Fields

Lab: Storing Energy in Non-Uniform Electric Fields (Part A)

There are two parts to this lab activity. The first part is a simulation that examines how a charged particle behaves in a non-uniform electric field due to the force caused by the field. The second part is a simulation that examines the energy transfer from kinetic energy and potential energy between the charged particle and the non-uniform electric field.

Part A: Motion in a Non-Uniform Electric Field

Purpose

In this part of the lab activity you will use a computer simulation to collect data enabling you to answer the following questions:

How does a test charge move in a non-uniform electric field?
How can this motion be explained using physics principles?

Procedure

Step 1: Open the Electric Field, Non-Uniform simulation. Once in the simulation, enter the following settings:

Place the particle (test charge) at (100, 0). This can be done by entering in the x and y values
Leave the Electric Field (Source Charge) at 3 mC, the Particle Velocity at 15 m/s at 0^o, the particle's charge at 2 mC and the particle's mass at 3 kg
Turn on the velocity vector
Press play and allow the simulation to play until the particle reaches (300, 0) or use the step button to advance the particle's motion until it reaches (300, 0).
Observe the particle's velocity («math xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mover»«mi»v«/mi»«mo»§#8594;«/mo»«/mover»«/math»or v_x) and velocity vector as the simulation plays or the particle's motion is advanced.

Analysis

Self-Check

Answer the following self-check (SC) questions then click the "Check your work" bars to assess your responses.

SC 1.

Describe the motion of the test charge. Is the motion uniform or accelerated?
Explain the motion of the particle using Newton's laws of motion.
Draw a free-body diagram to show the force acting on the particle at the starting point (A =100 m) and end point (B = 300 m)
Explain how the source charge was able to exert a force on the test charge even though the particles were not touching.

SC 2.

Calculate the magnitude and direction of the electric field of the source charge (+3.0 mC ) if it began at A =100 m and ended at B =300 m
Explain how your answers to the previous question demonstrate that electric field varies inversely to the square of the distance from the source.

SC 3.

Use your values for electric field from SC 2.a. to calculate the magnitude and direction of the electrostatic force acting on the test charge at locations A and B
Use your answers from SC 3.a. to calculate the acceleration of the test body at locations A and B. Verify that these values match a_x in the simulation.

Check Your Work

Self-Check Answer

SC 1.

Since the velocity is increasing, the motion of the test charge is accelerated motion.
The electrostatic force acting on the test charge pushes the test charge away from the source charge since both objects are positively charged. The electrostatic force is the only force acting on the particle; therefore, this force is an unbalanced force. According to Newton's second law of motion, unbalanced forces cause objects to accelerate in the direction of the unbalanced force.
The electric field of the source charge enabled it to exert a force on the test charge even though these charges were not touching.

SC 2.

a.

Given

Required

The electric field at 100 m, , and the electric field at 300 m,

Analysis and Solution

Since the source is positive, both electric field vectors are directed away from the source at an angle of 0°.

Paraphrase

The electric field at the location 100 m to the right of the source is [0°].

The electric field at the location 300 m to the right of the source is [0°].
The location that is 300 m from the source is three times further away than the location that is 100 m from the source. Therefore, the magnitude of the electric field is only as strong at the further location, compared to the closer location.