? Two equal charges are placed in a medium at a distance of 9 cm from ...
Given:
- Two equal charges are placed in a medium at a distance of 9 cm from each other.
- They exert a force equal to 4N on each other.
- One of the charges is increased by 6 microcoulomb.
- The distance between them has to be increased by 3 cm to keep the force between them the same.
To Find:
- The magnitude of charges.
- The dielectric constant of the medium.
Solution:Step 1: Calculate the initial charges on each object.
- Let the initial charge on each object be Q.
- Using the Coulomb's law, we can find the magnitude of the charge Q:
$$F = \frac{kQ^2}{r^2}$$
where F = 4N, k = 9 x 10^9 Nm^2/C^2, and r = 9 cm = 0.09 m.
Solving for Q, we get:
$$Q^2 = \frac{Fr^2}{k}$$
$$Q^2 = \frac{(4)(0.09^2)}{9\times 10^9}$$
$$Q = \sqrt{\frac{(4)(0.09^2)}{9\times 10^9}}$$
$$Q = 2.4 \times 10^{-8} C$$
Therefore, each object has an initial charge of 2.4 x 10^-8 C.
Step 2: Calculate the final charge on the object that was increased.
- Let the final charge on the object that was increased be Q1.
- The other object still has a charge of Q.
- Since the distance between them has increased by 3 cm to 12 cm, we can use Coulomb's law to find the new force:
$$F = \frac{kQ_1Q}{r^2}$$
where F = 4N, k = 9 x 10^9 Nm^2/C^2, and r = 12 cm = 0.12 m.
Solving for Q1, we get:
$$Q_1 = \frac{Fr^2}{kQ}$$
$$Q_1 = \frac{(4)(0.12^2)}{9\times 10^9(2.4\times 10^{-8})}$$
$$Q_1 = 2.0 \times 10^{-8} C$$
Therefore, the final charge on the object that was increased is 2.0 x 10^-8 C.
Step 3: Calculate the dielectric constant of the medium.
- Since the force between the charges remains the same even after increasing the charge on one object and increasing the distance between them, we know that the medium is a dielectric.
- To find the dielectric constant of the medium, we can use the formula:
$$k = \frac{1}{4\pi\epsilon_0}\frac{F r