Electric charge is a fundamental property of matter. There are two types of electric charge: positive and negative. Like charges repel each other, while opposite charges attract each other.
Coulomb's law describes the electrostatic force between two charged objects. It states that the force between two point charges is directly proportional to the product of their charges and inversely proportional to the square of the distance between their centers.
$$ F = k \frac{ |q_1 \cdot q_2| }{ r^2 } $$An electric field is a region around a charged object where another charged object experiences a force. The direction of the electric field is the direction of the force that a positive test charge would experience if placed in the field.
$$ E = \frac{ F }{ q_0 } $$Electric potential is the electric potential energy per unit charge. A positive test charge will have higher potential energy when placed in a region of higher electric potential. The potential difference between two points in an electric field is measured in volts.
$$ V = \frac{ U }{ q } $$Electric current is the flow of electric charge. The SI unit of electric current is the ampere (A), which is defined as the flow of one coulomb of charge per second.
Ohm's law states that the current through a conductor between two points is directly proportional to the voltage across the two points. The proportionality constant is the resistance of the conductor.
$$ V = I \cdot R $$In a series circuit, the components are connected end-to-end, and the same current flows through each component. In a parallel circuit, the components are connected across the same voltage source, and the voltage is the same across each component.