8. two +1 C charges are separated by 3000m. What is the magnitude of the electric force between them?

1000 N

Explanation:

The magnitude of the electrostatic force between two charged object is given by

where

k is the Coulomb constant

q1, q2 is the magnitude of the two charges

r is the distance between the two objects

Moreover, the force is:

- Attractive if the two forces have opposite sign

- Repulsive if the two forces have same sign

In this problem:

are the two charges

r = 3000 m is their separation

Therefore, the electric force between the charges is:

the answer is the first electromagnet (a). this is because it has more coils around the ferromagnetic material. increasing the number of coils increases the surface area in which the metal interacts with the current in the coil. this enables more atoms in the metal to become aligned hence becoming more magnetized.