One charge is decreased to one-third of its original value, and a second charge is decreased to one-half of its original value.

How will the electrical force between the charges compare with the original force?

It will increase to six times the original force.
It will increase to thirty-six times the original force.
It will decrease to one-sixth the original force.
It will decrease to one-thirty-sixth the original force.

1 answer

To evaluate how the electrical force between two charges changes when their magnitudes are altered, we can use Coulomb's Law, which states:

\[ F = k \frac{|q_1 q_2|}{r^2} \]

where \(F\) is the electrical force between two charges, \(k\) is Coulomb's constant, \(q_1\) and \(q_2\) are the magnitudes of the charges, and \(r\) is the distance between the charges.

Let the original charges be \(q_1\) and \(q_2\). The original force \(F_{\text{original}}\) can be expressed as:

\[ F_{\text{original}} = k \frac{|q_1 q_2|}{r^2} \]

According to the problem, the first charge is decreased to one-third of its original value, and the second charge is decreased to one-half of its original value. Therefore, the new charges are:

  • New \(q_1' = \frac{1}{3} q_1\)
  • New \(q_2' = \frac{1}{2} q_2\)

Now we can calculate the new force \(F_{\text{new}}\):

\[ F_{\text{new}} = k \frac{|q_1' q_2'|}{r^2} = k \frac{\left|\frac{1}{3} q_1 \cdot \frac{1}{2} q_2\right|}{r^2} \]

This simplifies to:

\[ F_{\text{new}} = k \frac{|q_1 q_2|}{r^2} \cdot \frac{1}{3 \cdot 2} = F_{\text{original}} \cdot \frac{1}{6} \]

This shows that the new force \(F_{\text{new}}\) is one-sixth of the original force.

Thus, the electrical force between the charges will decrease to one-sixth the original force.

The correct answer is: It will decrease to one-sixth the original force.