# Fundamentals of electronics - Ohm's law, Power, Electromotive force

When electric components are connected to each other to obtain a certain result, we have an electric circuit. Electric circuits can be described by using an appropriate symbolism for its components and the electric quantities involved. Every component reacts to the electric quantities that stimulate them according to certain rules. Through electric schemes and their associated formulae, we gain complete control over the functionalities of the circuit in question. In the following circuit we'll highlight how the application of voltage to the far ends of a resistance generates a current flowing through it. Simple circuit

Let's now take a look at some simple but important circuits, since more complicated circuits can be seen as exvoltages and elaborations of these simpler examples.

• Series circuit: in this type of circuit the whole current flow passes through each of the resistances: Circuit with resistors in series

The entire circuit has a total resistance value equalling the sum of the resistances in the circuit:

Equation 4.8. Equivalent resistance of two resistors in series  We can see how the total value increases when the resistances increase.

• Parallel circuits: in this kind of circuit, the current flow is subdivided into various parts each of which flows into one of the resistances. The lower the resistance, the greater the amount of current flowing through it: Parallel resistance circuit

The whole circuit has an equivalent resistance, given by the following formula:

Equation 4.9. Equivalent resistance of two parallel resistors   We can see how the total value decreases as the number of parallel resistors increases.

• Voltage divider: this type of circuit is used when we need to subdivide the main voltage into smaller voltages: Voltage divider

Equation 4.10. Formulae that describe the Voltage divider     #### Related topics on Wikipedia

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