Coulomb's Law Packet Coulomb's Law of Electrostatics states that ...

PhysicsCoulomb's Law PacketName:___________Coulomb’s Law of Electrostatics states thatwhere:F is the force measured in Newtonsk is Coulomb's constant which equals 9 x 10 9Q is the magnitude of each charge in coulombs (remember electrons and protons are -/+ 1.6 x 10 -19 C)r is the distance between the centers of the two charges in metersThis formula may only be used for charges that are small and round. That is, for isolated points of electriccharge. It is an example of an inverse square law. For example: if you double the distance between two chargesthen the force between them is reduced to ¼ of the original amount of force.If F is negative, that means that the charges carry opposite "signs" -- that is, one is positive and the other isnegative. The negative answer means that the point charges are attracting each other -- it does NOT actually tellyou in what direction the force is.If F is positive, that means that the charges carry the same "sign" -- that is, either both are positive or both arenegative. A positive answer means that the point charges are repelling each other -- it does NOT actually tellyou in what direction the force is.Coulomb’s Law is Essential in understanding the behavior of atoms which itself is vital in understandingchemistry and biology. Consider the hydrogen atom as a simple model below.Using Coulombs Law answer these questions:1. Which letter designates the electron orbiting the nucleus? A B2. Which letter designates the proton in the nucleus? A B3. Is the electron positively or negatively charged? _____________4. Is the proton positively or negatively charged? _____________5. The electrical interaction between the nucleus and the orbital electron is a force of( attraction repulsion ).6. If the charge of either the nucleus or the orbital electron were greater, the force between the nucleus and the electron would be(greater less ).7. If the distance between the nucleus and electron were greater the force would be ( greater less).8. If the distance between the nucleus and electron were doubled, the force would be1/4 as much 1/2 as much 2 times as much 4 times as much

Refer to the following information for the next ten questions.Two charges, a +3x10-5C charge and a -6x10-5 C charge, are 2 meters apart.9. What is the magnitude of the original electrostatic force between them? Show all work below.10. Is it an attractive or repulsive force? ________11. How could you change the situation to reverse your answer to #10 ? _______________________________12. How would the original force change if the charges were moved twice as far apart? ___________________Calculate the force below.13. How would the original force change if the charges were moved towards each other to a final distance which equals half of theiroriginal separation? _______________Calculate the force below.14. How would the original force change if the charges were each doubled in size? _________________Calculate the force below.15. How would the original force change if each of the charges were to be cut in half? ________________Calculate the force below.

16. How would the original force change if the charges were each doubled in size as well being moved to a distance that is twice theiroriginal separation? Explain.17. Which of the following combinations of changes, involving both a change in the magnitude of the charges as well as theirseparation, could produce a force that is 64 times stronger than the original force between them?a) you could quadruple each charge and also move them to new positions which represent a distance that is only half of their originalseparationb) you could cut each charge in half and also move them to new positions which represent a distance that is 16 times greater than theiroriginal separationc) you could double one charge, quadruple the second charge and move them to new positions which represent a distance that is 8times greater than their original separationd) you could double each charge and also move them to new positions which represents a distance that is only one-fourth their originalseparationjustify your choice with a calculation18. One Coulomb is actually an incredibly large amount of unbalanced charge. To see why imagine you have two Styrofoam ballsleft over from when you had to make a model of the solar system. If one coulomb of charge were placed on each ball, how far apartmust the two balls be so that the force on these two balls is only 1 N (which is not very much force, it’s the weight of a small apple).Convert your answer to miles.19. Two spheres A and B are charged so that A has twice the charge of B. The force between the two spheres is 0.5 N and they are0.60 m apart. Find the charge of A and B. (Hint: call the charge of B “Q”)20. A nucleus of uranium contains 92 protons.A) What is the charge in Coulombs of 92 protons?B) If two of these nuclei experience a force 0.22 N how far apart are they?

Sample Problems:Given:Q1= 6.4 x 10 -7 CQ2=7.3 x 10 -7 CFelectric 0.3 Nk 9 10 9 Nm 2 /C 2Unknown: r ?Equation:Solve for r:and thenSubstitute the values and solve:=0.12 m2. Suppose you place equal but opposite amounts of charge at the Earth’s North and South Poles. How much charge isat each pole if the magnitude of the electric force compressing Earth is 5.17 10 5 N? Earth’s diameter is 1.27 10 7 m.Given:Felectric 5.17 10 5 Nr 1.27 10 7 mk 9 10 9 Nm 2 /C 2Unknown: q ?Equation:Solve for Q since they are equaland then rearrangeand finallySubstitute the values into the equation(s) and solve:Even though the force is attractive (-) we don’t put the minus sign into the equation because we really don’t know what direction theforce is.