Coulomb\'s law states that the electric force between two point charges acts alo
ID: 1596293 • Letter: C
Question
Coulomb's law states that the electric force between two point charges acts along the line joining the charges. (A point charger is a charge that's small enough to be treated as if it were all located at a single point.) The magnitude of the force on either of the charges is proportional to the product of the charges and is inversely proportional to the square of the distance between the charges. A. Two positive point charges + q and +Q (with |Q| > |q| are held in place a distance s apart. 1. Indicated the direction of the electric force exerted on each charge by the other. 2. Is the force on the +q charge by the +Q charge greater than, less than, or equal to the force on the +Q charge by the +q charge? Explain. 3. By what factor would the magnitude of the electric force on the +q charge change if the charges were instead separated by a distance 2s? B. Two more +Q charges are held in place the same distance s away from the +q charge as shown. Consider the following student dialogue about the net force on the +q charge: Student I: "The net electric force on the +q charge is now three times as big as before, since there are now three positive charges exerting forces on it." Student 2: "I don't think so. The force from the +Q charge on the right. The net electric force will be same as in part A." 1. Do you agree with either student? Explain. 2. Indicate the direction of the net electric force on the +q charge. Explain 3. What, if anything, can be said about how the magnitude of the net electric force on the +q charge changes when the two +Q charges are added? Explain.Explanation / Answer
A)
1) Since, similar charges repel each other
Force on +q is directed upwards
Force on +Q is directed downwards
2) Both forces are of same magnitude
3) Since, force is inversely proportional to square of distance betweeb the charges, it will decrease 4 times.
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B)
1) Both the statements are incorrect
The net force acting on +q will be the vector sum of the forces due to the three +Q charges
2) By the symmetry in the diagram, we can conclude that the horizontal component of forces will cancel each other
and the net force will be directed upwards.
3) Let F be the force due to any one +Q charge.
Then, the net force will be greater than F but less than 3F