(EEM) Electricity and Circuits Lesson

Electricity and Circuits

Electric circuits are all around you, and they play a major role in your everyday life. There are many circuits in the electronic devices that you use such as your television, your cell phone and the appliances in your home. An electrical circuit is a network consisting of a closed loop, giving a return path for electrical current. Electric circuits are similar to the roads that we drive on in that they provide a path for electrons to flow just as a road provides a pathway for cars. An electric circuit is usually composed of a voltage source (like a battery), a conductor (such as wire), a switch that can open and close the circuit and components (the load) that use the energy flowing in the circuit. Circuits can contain other components, but this is a general model that we will use in our discussion.

Before we discuss electric circuits in detail we must understand the electricity that flows through them. Electricity is the flow of charged particles through a conductor that has the ability to do work. We measure several aspects of electricity and we assign specific units of measurement to describe them. Electricity flows in a current, which is made up of electrons moving through a conductor. You can think of current as being similar to water flowing through a water hose. As more water leaves the hose, the amount of current measured increases. With electricity the more electrons that flow through a wire determines the amount of current flow. Current is measured in units called the Ampere, which is sometimes abbreviated as Amp (A). The higher the amperage the more current there is flowing through the wire. Current is the component of electricity that determines how much work can be done by electrical energy. Another component that we have to take into account is the amount of resistance to current flow that exists in a wire or component. Some materials allow electrical current to pass through them very easily while others resist the flow of electrons. The amount of electrical resistance that a substance produces is measured in Ohm's (Ω). In order to generate an electrical current there has to be a potential difference between two points that provides the pressure needed to cause the movement of electrons. Looking back at our water hose example, we can equate this potential difference to the amount of water pressure in the hose. The higher the pressure the faster the current flows. With electrical current we measure this potential difference as volts. Voltage is the potential difference in charge between two points. The higher the potential difference between two points, the more current that can be generated. We can show this relationship in a formula that describes how voltage, current and resistance are related. This is known as Ohm's law.

Ohm's Law

$I=\frac{V}{R}$

I = Current (ampere)

V = voltage (volts)

R = Resistance (Ohms)

 

As you can see from the formula, as voltage increases, current increases as well. Let's look at a problem involving the use of Ohm's law.

If I have a circuit with a resistance of 100 Ω that is connected to a 12 volt battery, how much current is generated in the circuit?$\text{I}= \frac{12\text{v}}{100\Omega}=12\text{A}$

Circuit Types

Series

There are two major types of circuits that are distinguished by how the electrons flow through the conductor in the circuit. A direct flow of electrons from the energy source through several components create a series circuit. In a series circuit, there is only one pathway for electrons to flow, and the same current travels through all of the components. In this arrangement, each component provides resistance and drops the voltage the next component receives. For example, if six light bulbs are arranged in a series circuit and connected to a 12 volt battery each bulb will cause the voltage to drop before reaching the next component. In this case, the actual voltage each bulb would receive is 2 volts. In a series circuit the current travels through each component before entering the next. If one component is disabled, then the rest of the components will not receive current and will not function.

Parallel

A circuit consisting of several different pathways for electrons to flow is called a parallel circuit.  In a parallel circuit, the voltage is the same for every component. Each component receives the full voltage. For example, if six light bulbs are arranged in a parallel circuit and are connected to a 12 volt battery, each light will receive 12 volts from the energy source. The advantage to using a parallel circuit is one component can become disabled while the rest of the components can still function. For example, if you have a set of lights arranged in a parallel circuit and one of the bulbs stops working, the rest of the light will still remain operational. The disadvantage to using a parallel circuit is when you add more components to the circuit, it requires more current to make them function. This decreases the life of a battery that is powering the circuit.

As you can see, there are several types of circuits that carry electrical current. Each type has its advantages and disadvantages which determines the type of circuit used in an application. Electrical circuits are such an integral part of our life that we would not know how to live without them in a modern world. The next time you use an electronic device think about the circuits that make it possible and the technology involved in creating them.

[CC BY 4.0] UNLESS OTHERWISE NOTED | IMAGES: LICENSED AND USED ACCORDING TO TERMS OF SUBSCRIPTION