Answer:
a.Electric force exerted on one charged sphere, by another charged sphere.
Step-by-step explanation:
Coulomb's Law describes the electric force between two objects. It is given by the following formula:

The magnetic field surrounding a current carrying conductor is described by Ampere's Law.
Amount of heat generated by a high current flow in a resistor can be described by P = VI
Voltage induced in a coil by a constant magnetic field is described by Faraday's Law.