Coulomb's law worksheet

Name: ____________________________ Date: _________________ Coulomb’s Law LAB This lab uses the PHET Gravity Force Lab located at https://phet.colorado.edu/en/simulation/coulombs-law THEORY The idea of electrical forces has been known since ancient times, with static electricity being discovered the by Greeks. However, generating static electricity was difficult to do with precision. Sometimes you got more electric charge and sometimes less electric charge, so determining the nature of electric forces was difficult to do in detail. By the 18th Century, however, scientists had developed ways of generate and store considerable and reproducible static electric charges. This led to a more thorough understanding of the nature of static electricity. In 1785, a French natural scientist named Charles Augustin de Coulomb published a paper describing the relationship between electric charge and the forces produced by those charges upon one another. The mathematical description of that relationship has come to be known as Coulomb’s Law. This law is written today as F e =k e q 1 q2 r2 where Fe is the electrostatic force, the q’s are the charges, r is the separation between the charges, and ke is the electrostatic constant (sometimes called the Coulomb constant). The electrostatic constant has been determined to be given by k e=8.98755179×109 N⋅m2 . C2 Coulomb’s law has been tested over as far a range in sizes and configurations as physics allows, and it seems to hold in all cases. That includes from sub-atomic sizes to astronomical sizes. For spherically symmetric systems, the term r is taken as the distance between the center of one spherical charge to the center of another spherical charge. The computer lab simulations allows you to study Coulomb’s Law by adusting three variables: the the charge of the object on the left, the charge of the object on the right, and the distance between the objects. It then displays the force between the objects. You may elect to display the force in decimal form or scientific notation (whichever may be easiest for you to write down). The charges may be changed by adjusting the charge sliders below the ruler. You can click on each charge and move it to change the distances between the charges. PROCEDURE: Go the simulation web site: https://phet.colorado.edu/en/simulation/coulombs-law Click to run the lab (it is HTML5 coded, so it should run in any modern web browser). Choose the “Macro Scale” to do the experiment. You may elect to display the force in decimal form or scientific notation (whichever may be easiest for you to write down). The charges may be changed by adjusting the charge sliders below the ruler. You can click on each charge and move it to change the distances between the charges. Investigation One: 1) Adjust each charge to +5 μC. Move charge one to the 4 cm x position. Place charge two at the 6 cm x position. Record the direction and magnitude of the force between the charges in data table one-a (notice that the forces should be equal and opposite). 2) Now, adjust Charge 2 to be equal to zero. Record the magnitude and direction of the forces. 3) Now, adjust Charge 2 to be -5 μC. Record the magnitude and direction of the forces. 4) Leaving Charge 2 as -5 μC , adjust Charge One to 0 μC and then -5 μC, recording the magnitude and direction of the forces. 5) Take note of what you see here. You will be expected to comment on the results in the post-lab questions. 6) Place Charge One at the 3cm mark. Place Charge Two at the 7 cm mark. Next, adjust Charge One to 1 μC and Charge Two to 4 μC. Record the magnitude and direction of the forces in data table one-b. 7) Adjust the Charge One to 4 μC and Charge Two to 1 μC. Record your results 8) Adjust the Charge One to 2 μC and Charge Two to 2 μC. Record your results in data table onec. 9) Adjust the Charge One to 4 μC and Charge Two to 4 μC. Record your results. 10) Adjust the Charge One to 8 μC and Charge Two to 8 μC. Record your results. Investigation Two: 1) Adjust each charge to +5 μC. Move charge one to the 0 cm x position. Place charge two at the 2 cm x position. Record the magnitude of the force in data table two. 2) Move mass two to the 3 cm position. Record the force. 3) Continue moving mass two at one centimeter intervals, recording the forces. 4) Compute r, the distance between the masses, in meters. Then compute compute 1/r2. 5) Plot F vs 1/r2.