Chapter 32, Problem 25A

Indicated below are pairs of electric charges in three different arrangements. In each figure, a test charge is located at the point labeled P. The other, much larger, charges all have the same magnitude and lie on a line that passes through P. Note some charges are positive and some are negative. Rank the arrangements on the basis of the strength of the electric force on the test charge, from strongest to weakest.

To determine

To rank: The arrangements on the basis of strength of the electric force on the test charge, from strongest to weakest.

Answer to Problem 25A

C > B > A

Explanation of Solution

Introduction:

Opposite charges attract each other. Also, protons are heavier in mass. Thus, exerts a stronger force on other nearby particles.

The given arrangement is shown below.

  

In each arrangement, at point P test charge is located.

Here, in arrangement C, a test charge is placed in between proton and electron. Since both particles are of opposite charge. Thus, protons and electrons will attract each other. But, the force exerted by protons will be higher due to heavier mass. Thus, it will attract not only test particle but also electron and have the strongest force on the test charge.

In arrangement B, test charge is placed at the other end from the proton. Here proton will exert the same attractive force on the electron and also on the test charge. But, here force experienced by the charged particles will be lesser.

In arrangement A, the test charge is placed in between two repelling particles i.e. electrons. Both electrons will repel each other. Thus, the net force experienced by both the electrons will be too less compared with the other two arrangements.

Conclusion:

Thus, ranking from strongest to weakest is C > B > A.