## What are the basic components of a circuit?

The basic circuit components include resistors, transistors, inductors, diodes, switches, capacitors, ground, and other sources. The **conductive wires **or traces connect all the components to each other and form a **loop **for the current to flow through.

Component | Description |

Transistor | A semiconductor electronic component that may be used to amplify, generate, or switch electrical signals or power in circuits. |

Inductor | Also known as the coil or choke. It is made from a coil of insulated wire and is commonly used in switched-mode power systems to create direct current (DC). |

Diode | A semiconductor device that functions as a one-way switch for current. It lets current flow freely in one direction whilst significantly restricting current flow in the other direction. |

Switch | A component that manages the flow of electric current inside a circuit. |

Capacitor | A type of electronic component that stores potential energy in the form of electricity. Capacitors store potential energy by holding positive and negative energy on two conductive plates separated by a dielectric material. This produces a potential difference between the two plates. |

Ground | The reference point from which voltages are measured. At the ground point, the voltage value is zero. |

Sources | Sources are the components that supply current, voltage, or power. |

Resistor | A two-terminal passive electronic component that acts as a circuit element by implementing electrical resistance. |

Measuring components | These are mainly referred to as voltmeters and ammeters. The voltmeter is a device that measures the voltage differences between two points in an electric circuit. The ammeter is a component that measures electric current in amperes, either direct or alternating. |

Below we focus on resistors and sources for you to get the fundamental knowledge about electrical circuits.

### Resistors in circuits

A resistor is a two-terminal passive electronic component that acts as a circuit element by implementing **electrical ****resistance**. Resistors are used in electronic circuits for various purposes, including **reducing current flow**, adjusting signal levels, dividing voltages, biassing active components, and terminating transmission lines.

The two symbols for a resistor in a circuit, Oğulcan Tezcan – StudySmarter Originals

Here is **Ohm’s law** for calculating the resistance:

\[R =\frac{V}{I}\]

V stands for voltage in volts, I is for current in amperes, and R is for resistance in ohms.

The **variable resistor **is another component that allows us to **control ****how much current flows across a circuit. **It operates by moving a **wiper terminal **over a resistive substance, which is usually a thin film, a chunk of carbon, or a resistive wire composed of nickel-chromium or tungsten alloys.

The symbol of a variable resistor in a circuit, Oğulcan Tezcan – StudySmarter Originals

### Sources in circuits

Three types of sources are used in electric circuits: current source, AC (alternating current) voltage source, and DC voltage source.

- A
**current source**is an electronic component that either**provides or absorbs electricity**. There are two types

- An AC power source is a device capable of supplying
**alternating power****and****frequency**to a load. An AC power’s graph has the shape of a**sine wave**where the**frequency**is measured by period per second.

- DC voltage source is a device capable of supplying
**constant****voltages****and currents**to the circuit.

The symbols for a current source, AC power source, and DC voltage source, Oğulcan Tezcan – StudySmarter Originals

While the values you see next to the current source and the DC voltage source are **constant**, the value you see next to the AC power source is the **value of the sine wave’s amplitude**.

## What are the types of circuits?

There are **five** **main types **of circuits: closed circuit, open circuit, short circuit, series circuit, and parallel circuit. Each of these is designed to create a **conductive path** for current flow.

- An
**open circuit**is a circuit that has**no current flowing**through it. The circuit’s continuity is interrupted, and the current does not flow as a result. An open circuit is any circuit that does not pass current when a potential difference is created, and its**resistance is****infinite**.

- A
**closed circuit**is a**complete electrical connection**around which current flows or circulates. A closed circuit is formed when a succession of electrical wires connects to each other and completes a circuit, allowing electricity to flow from one end of the circuit to the other.

- A
**short circuit**is an**improper connection**between two nodes with voltages that are supposed to be different but aren't. In an ideal short circuit, this implies that there is**no resistance****and no voltage drop**across the link. The outcome in actual circuits is a connection with**nearly no resistance**. When there is almost no resistance, all the current going through the conductive wire travels through the short circuit and reaches**high levels.**This can cause the conductive wire to burn out.

The section below focuses on series circuits and parallel circuits for you to get the fundamental knowledge about electric circuits.

### Series circuit

A series circuit is a circuit in which the **entire current **passes through all components **without dividing**.

An example diagram of a simple series circuit Oğulcan Tezcan – StudySmarter Originals

#### Calculating the total voltage in a series circuit

The **same amount of current** goes through all the components without dividing in a series circuit. To calculate the **total voltage** in a series circuit, we use this equation:

\[V = V_{R1}+V_{R2} + V_{R3}\]

V is the voltage value of the DC voltage source. V_{R1}, V_{R2}, and V_{R3} are the voltage values of the resistors.

#### Calculating the total resistance in a series circuit

Here is the equation for calculating the total resistance:

\[R_{Total} = R_1 +R_2+R_3\]

R_{Total} is the total value of resistance in ohms. R_{1}, R_{2}, and R_{3} are the resistance values in ohms.

#### Calculating the total current in a series circuit

The total current in series circuits is the **same value as the individual current** for all components. You can define it as:

\[I_{Total} = I_1 = I_2 = I_3\]

I_{1}, I_{2}, and I_{3} are the values of the current going through R_{1}, R_{2}, and R_{3} in amperes.

### Parallel circuit

A parallel circuit has branches that **divide the current **so** **that just a portion of it travels through each branch. In a parallel circuit, the **voltage (or ****potential difference) between each branch is the **** same**, but the currents may vary.

An example diagram of a basic parallel circuit, Oğulcan Tezcan – StudySmarter Originals

#### Calculating the total voltage in a parallel circuit

The total voltage in parallel circuits is the **same value as the individual voltage for all ****branches**. You can define it as:

\[V = V_1 = V_2 = V_3\]

V is the voltage value of the DC voltage source. V_{1}, V_{2}, and V_{3} are the voltage values of the resistors on the different branches.

#### Calculating the total resistance in a parallel circuit

To calculate the total resistance in a parallel circuit, we use this equation:

\[\frac{1}{R_{Total}} = \frac{1}{R_1} + \frac{1}{R_2} + \frac{1}{R_3}\]

R_{Total} is the total value of resistance in ohms. R_{1}, R_{2}, and R_{3} are the resistance values of the resistors in ohms.

#### Calculating the total current in a parallel circuit

Here is the equation we use for calculating the total current in a parallel circuit:

\[I_{Total} = I_1 + I_2+I_3\]

I_{1}, I_{2}, and I_{3} are the values of the current going through R_{1}, R_{2}, and R_{3} in amperes.

#### Calculating an individual resistance’s current in a parallel circuit

If you want to calculate an **individual ****resistance’s ****current **in a parallel circuit, there is a shortcut! Let’s calculate R_{1}’s current from the above diagram.

Let us say the total resistance R_{Total} of R_{2} and R_{3} is R_{p}, which we can find as shown below.

\[\frac{1}{R_P} = \frac{1}{R_2} + \frac{1}{R_3}\]

We can then put this value in our shortcut equation and find the current value of R_{1}. This is also known as a **current ****divider**.

\[I_1 = \frac{R_P}{R_1+R_P} \cdot I_{Total}\]

The total current in series circuits is the **same value as the individual current** for all components.

The total voltage in parallel circuits is the **same value as the individual voltage for all ****branches**.

## Circuits - key takeaways

- An electrical circuit is a collection of interconnected electronic components.
- The basic components of an electric circuit are sources, ground, resistors, inductors, diodes, capacitors, switches, and transistors.
- The five main types of electric circuits are closed circuits, open circuits, short circuits, series circuits, and parallel circuits.
- An open circuit is a circuit that has no current flowing through it because of an interruption.
- A closed circuit is a complete electrical connection around which current flows or circulates.
- The main difference between a series and parallel circuit is that whilst the current is not divided in the series circuit, it is divided into branches in a parallel circuit.

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##### Frequently Asked Questions about Circuits

What is a circuit?

An electric circuit is a collection of interconnected electronic components.

What is a circuit breaker?

A circuit breaker is a safety device that protects an electric circuit when there is too much current or a short circuit.

What is a series circuit?

A series circuit is a circuit in which the entire current passes through all of the components without dividing.

What is a parallel circuit?

A parallel circuit is a circuit that has branches that divide the current so that just a portion of it travels through each branch.

What is a short circuit?

A short circuit is an improper connection between two nodes of an electric circuit with voltages that are supposed to be different but aren’t.

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