Electricity & Megnetism

Electric circuit

Electrical circuit is a connection of devices, such as generators, resistors, receivers, capacitors, inductors, etc., made by means of a conductor wire, which allows the passage of electrical charges through the circuit elements. The electric current passes through the circuit thanks to the application of an electric potential difference, produced by a voltage source.

Elements of electrical circuits

Electrical circuits can contain a large number of different elements, with different functions, such as producing heat, storing electric charges, interrupting the flow of electric current, etc. Let’s check out some of the most important elements present in electrical circuits.

Generators : transform various forms of energy into electrical energy . The main function of the generator is to cause a potential difference between the terminals of electrical circuits so that electrical current can flow. Batteries, batteries and outlets are examples of generators .

The generator is symbolized by two parallel bars of different sizes.
  • Resistors : dissipate electrical energy exclusively in the form of heat. This phenomenon is known as E made Joule . The greater the electrical resistance of the resistor, the smaller the electrical current flowing through it. Electric pans and flat irons are examples of resistors.
Resistors are usually represented with a zigzag
  • Receptors : convert electrical energy into kinetic energy. The fan, the mixer, the blender, the air conditioner and the refrigerator are examples of receivers, because, inside them, there is an electric motor that produces movement or that compresses some type of gas. The symbol used to represent receivers is the same as the symbol for generators, however, in receivers, electrical current always flows from the lowest electrical potential to the highest electrical potential.
The electric motor, like the one shown in the picture, is a type of receiver.
  • Capacitors : store electrical charges when subjected to some potential difference. They are used in most electrical circuits, both for storing charges and stabilizing the flow of electrons in the circuit.
Capacitors are represented by two parallel bars of the same size.
  • Control devices: are used to measure different parameters of the circuit, such as electrical voltage and electrical current. Ammeters , voltmeters and multimeters are examples of control devices.
A multimeter is a device used to measure electrical voltage and current.
  • Safety devices: Provide a mechanism to interrupt the electrical current if it exceeds the safety limit. The fuse and circuit breaker are safety devices.
Fuses are usually represented by a rectangle crossed by a horizontal line.

Types of electrical circuits

There are simple electrical circuits , which are those with only one electrical device, which is directly connected to a generator by means of conducting wires, but there are also electrical circuits in which there is more than one element, in this case, forming more complex circuits. These more complex circuits can be classified into: series , parallel or mixed circuits (when there are series and parallel connections in the same circuit).

  • electrical circuit in series

In a series electric circuit, the elements are connected on the same wire and there is only one path for the electric current to flow. For this reason, the electric current is equal in all elements of the circuit . The same cannot be said about the electric voltage, which drops as the electric current passes through these elements

In a series electrical circuit, the elements are connected along the same wire.

→ Electric circuit in parallel

In parallel electric circuit, there are at least two paths in which electric current can flow. In this case, all the elements that are connected in parallel are submitted to the same voltage, however the current that passes through each wire depends on the electrical resistance of the element that is in each wire.

In addition to series and parallel circuits, there is mixed circuit. In mixed circuits, there are devices connected both in series and in parallel on the same branch (wire).

Exercises solved on electrical circuits

Question 1 — Choose, among the options below, the one that presents a control device.

a) receiver

b) Capacitor

c) resistor

d) ammeter

e) fuse


Letter D. Control devices are those that we use to measure some electrical characteristic of circuits, such as voltmeters and ammeters.

Question 2 — Indicate a safety device used in electrical circuits.

a) Generator

b) circuit breaker

c) receiver

d) Capacitor

e) Inductor


Letter B. The circuit breaker is a safety device that works according to the temperature rise in the conductor wires of electrical circuits. 

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