Electronics

Ohm’s law and an understanding of power forms the basis for understanding more about electrical circuits. The electric current flowing through a circuit will generate power, but the path that the current flows may be of two types: series or parallel. In series circuits current passes through every resistor to return to power. In parallel circuits the main circuit is divided into separate paths. This is most recognizable in holiday lighting; when one bulb causes the others to also go out representing a series circuit; and when only that bulb goes out reflecting a parallel circuit.

The diagrams here show circuits within a series and parallel system.

An electronic system may have a combination of series circuits and parallel circuits in order to manipulate the power of the current for a variety of reasons. Overall, the design for the electric current would be to optimize the power supply, while also limiting the chances for error.

Electricity can create heat energy and systems are wired to prevent damage to a system in the events that an electronic produces too much heat to operate properly. A fuse is a safety device within a system that contains a strip of wire designed to melt if a current exceeds a specific value. The fuse would melt and open the circuit, stopping the flow of electricity. A blown fuse may require repair work to the system, but it is likely less costly than the potential damage of an electrical fire.

Ground Level

Electricity can be considered potential energy. The potential energy that something has is measured in relation to another point. For example, an object being tossed from the roof of a building has potential energy in relation to its lowest possible point, the ground. Electricity’s energy maintains that same relationship.

Voltage is a measurement in relationship to the ground because the ground is considered to have a limitless ability to absorb a current. Electricity is the flow of electrons in a continual circuit, but when lightning strikes the ground with one million volts of electricity, the earth does not become electronically charged. This is why electronic systems may be grounded, so that their wiring has a mechanism to absorb extra electricity for safety reasons.

It is important to understand that the ground does not have a zero charge. Ground simply has the capability to absorb energy, but the earth emits a positive energy. Since electrons are negatively charged, electricity is attracted to the ground. Additionally, electrons are constantly seeking to travel in the path of least resistance which is why electricity is attracted to anything that will allow for the quick and continual flow of electrons. Materials such as metal and water assist the flow of electricity.

Since humans are made up of a large amount of water, humans can carry electricity. In some cases, we carry a small amount and emit it in the form of a shock when we touch something that can also carry electricity. In a more extreme example, lightning would want to send its current through the human body to assist its current in reaching the positively charged ground. This is why humans would want to distance themselves from the ground by being in a car, or take shelter during a lightning storm. If shelter is unavailable, people should shelter themselves underneath a large metal bridge because it would be a more optimal path for electricity to flow.

Power Supply

Circuits are continuous loops that allow for the flow of electricity to power an electronic system. The speed and direction may vary depending on the current. A current can be measured with an ampere meter, or ammeter. Other instruments used to measure smaller currents are milliammeters, which measure milliampere (mA), and microammeters, depending which function on the microampere (μA) range. A milliampere is one thousandth of an ampere. A microampere is one millionth of an ampere.

An alternating current (AC) power supply varies with time and is constantly changing. The constant changing makes it easier to obtain higher voltages which is necessary when trying to supply large amounts of electrical energy with the most efficiency. With an AC power supply, the frequency that the current changes direction per second is measured in a value of hertz (Hz).

This is in opposition to a direct current (DC) power supply which always flows in one direction. Since a direct current has fixed amplitude and no frequency, it is much easier to store electricity in this form. A simple way to think about DC power is in the form of a battery.

BE CAREFUL!
While the flow of electricity will operate from the positive to negative terminals of a battery, current is based on the flow of electrons. Electrons will always flow from the negative terminal to the positive terminal. Diagrams may note the direction of a current flowing from a negative to a positive terminal, while a majority of battery diagrams illustrate the direction from the positive terminal to the negative. Both types of illustrations are correct as long as the current flow is consistent. The effect of the powered system will remain the same.

A battery contains multiple cells. The cells store chemical energy that is converted into electrical energy when in use. When the battery supplies the electrical current, it is in a one-way flow. Electricity will flow from the positive terminal to the negative terminal.

Wire Materials

When electricity flows across a wire, the electrons may speed up or slow down. The pull of the positive charge increases speed and will cause the wire to create heat energy, but the electrons also have the potential to collide. The electrons will transfer portions of their energy and cause the atoms to slow down. Collision causes electrical resistance, which can be induced by the type of wire.

Wires are one of the essential components to a circuit. Wires must be made of specific materials in order to create a functional circuit. For example, using a cotton piece of cloth to connect terminal ends of a battery will not trigger the use of its electric energy. All materials can be classified as one of three categories: conductors, semiconductors, or insulators.

Conductors are materials with low electrical resistance, usually metals or elements from the transition metals groups of the periodic table. Wires made of these materials are considered good conductors because these elements have free electrons which allow for the electrons of the current to easily travel across the wire. The best-known conductors are copper, aluminum, and solder (tin or lead).

Semiconductors are materials with a mid-range electrical resistance. The material still allows for the continual flow of the current, but its conductivity speed is not as quick as conductor materials. This is due to the electrons within the material being more tightly bound and causing an increased resistance in comparison to conductors. However, thermal energy may have the ability to overcome this level of resistance depending upon the semiconductor. The most common materials used as semiconductors are silicon, germanium, and gallium arsenide.

A transistor amplifies a current and requires little power. It is considered a semiconductor. A common example is a transistor radio.

An insulator is a material with a high electrical resistance, otherwise considered a non-conductive material. Wires cannot be made of insulators because they simply do not allow for the flow of electricity and would otherwise prevent the flow of the current within a circuit. These materials include glass, plastics, rubber, and ceramics.

Insulators are important because they are used for protective measures when creating electrical systems. Insulator materials are used to wrap wire systems which separate electrical conductors without allowing for the current to pass through. If you’ve ever noticed the wiring in a home, individual wires are wrapped in special tubing to individualize the wire. Additionally, wires usually follow a non-conductive material like wood within the framework of a building to extend a power supply without risk of causing circuit mishaps or electrical fire. The alternative would be to have multiple wires wrapped together, which may combine circuits and cause extreme error.

Resistance

The material of a wire may reduce or increase resistance, but other factors such as the length and area of the wire may affect resistance as well. Resistance increases as the length of the wire increases. This is because the travel distance of the current has increased. The opposite effect occurs when the area, or width, of the wire increases. The larger the area of the wire, the lower the resistance is for the current because the larger cross-sectional area has increased the area the electrons can flow through.

Taking all of these factors into account, there are a few fundamental circuit rules to consider when calculating the resistance. Recall that in a series circuit, the current must flow through every resistor because the circuit is one continual loop. As a result, the total resistance is equal to the sum of the resistors.

Within a parallel circuit, the current can flow along multiple paths in order to increase the current and lower the resistance. The total resistance is equal to the sum of the resistor reciprocals.

These resistors allow for the current flow to be manipulated, but it is important to understand that the current is still consistent throughout the whole circuit.

Example

What will the voltmeter read that is connected to the circuit below?

A. 0 volts

B. 25 volts

C. 50 volts

D. 75 volts

D. The resistors are in a series. The voltage will be a sum of the voltages across the resistors. V = (I × R₁) + (I × R₂) = (5 amps × 10Ω) + (5 amps × 5Ω) = 50 volts + 25 volts = 75 volts. See Lesson: Electronics.

Resistors are coded with colors in order to indicate their value, tolerance (percentage error in the resistor’s resistance) and many times, quality.

The following chart provides an overview of the color code.

Electricity and Magnetism

Electric currents encourage the flow of electrons and that movement gives rise to magnetism, or a physical phenomenon produced by the motion of electric charge. The result is the attractive and repulsive forces between objects. For example, the opposite poles of magnets are attracted to one another, but their like poles actually repel.

Electromagnetism is defined as the interaction between electric currents and magnetic fields. Electromagnetism is one of the four fundamental forces in nature. It is responsible for electromagnetic radiation such as light.

BE CAREFUL!
The color code system above is used to provide information about resistors. This information does not transfer towards electrical wire color codes. While resistors have colored bands to provide information, the color of an entire wire will also provide information about what type of power the current carries. A green wire indicates the grounding of an electric circuit. Other colors indicate hardwiring (red) or more uncommon power sources (yellow and blue). Neutral colors (white or gray) indicate a neutral wire while black indicates power used in all circuits such as common sources like plug outlets.

Wires can form a coil when they are wrapped around a core material. The coil, considered an inductor, will have an electric current running through it. It will carry certain magnetic effects depending on a number of factors including the number of turns, how close those turns are, the strength of the current, and material of the core. If the coil is wrapped tightly to have an increased number of turns and also place each turn closer together, the magnetic field strength will increase. The magnetic field strength will also increase if the flow of the current is increased.

DID YOU KNOW?
A compass contains a small magnetic pin in order to respond to the planet’s magnetism. A direct current (DC) magnetic field stems from the ground naturally, causing a compass to point in the northern direction.

The material of the core can greatly influence the field strength. A soft iron core increases the field strength because the core offers resistance to magnetic flux. For example, iron offers less resistance to magnetic flux which increases the strength of the field. Electromagnetic induction is created when a conductor material is used in combination with a magnetic field in order to manipulate the flow of the current. The current will not flow if the conductor is motionless, but the current is induced if the conductor is moving through the magnetic field.

Transformers are created when two coils of wire are connected by an iron core and utilize the magnetic field to transfer energy between the coils. They are used specifically to alter an AC voltage.

Other Electrical Components

Electronic systems may have several additional components to the circuits. Circuits may contain notable components such as contacts, capacitors, as well as diodes.

KEEP IN MIND . . .
An electric generator will use electromagnetic induction to transform mechanical force into an electric current. A motor uses the same process to produce the reverse effects and transform an electric current into a mechanical force.

Electrical contacts are a safety switch which uses another low-voltage power source to complete or break a circuit as a safety precaution. They are not meant to prevent damage with a short-circuit like a breaker system. Rather, they use coils and electromagnetic current to either keep the circuit operating or interrupt it.

Capacitors, or condensers, store energy in an electric field. Two electric plates that can hold positive or negative charge will be separated by an insulator between them. A battery will power the electric field to charge the plates, but no current can flow through after a certain threshold. Instead, AC voltage can cause flow which is why capacitors are largely used for blocking direct current and allowing alternating currents.

A diode is a valve-like electrical component that maintains the flow of electricity in one-direction. The most common examples are LED lights.

The following diagrams show the symbols used to represent electronic components in circuitry:

Let’s Review

• Electricity is the flow of electrons and is a form of energy. It can flow through a circuit made up of wires, switches, and other components.
• A circuit must be a continuous loop for electricity to flow. Electricity will encounter resistance within a circuit.
• Voltage measures the potential energy between two points of a circuit. It is defined by Ohm’s Law: Voltage = Current × Resistance
• Power is the rate at which word is done. It can be measured by Power = Voltage × Current
• The materials used to create a circuit can speed up or slow down the flow of electricity. Materials can be classified as conductors, semiconductors, or insulators.
• Electricity gives rise to magnetism and coils use magnetic forces to manipulate current.
• Circuits may have a variety of other components. Circuit components may be represented with symbols to diagram the flow of a current.