Electricity is the presence and flow of electric charge. Using electricity we can transfer energy in ways that allow us to do simple chores. Its best-known form is the flow of electrons through conductors such as copper wires.
The concept of electricity can not be well taught without introducing its three most basic components. The basic components of electricity are:
- Voltage: The potential difference that exists between two points. Think of it as the pressure that pushes water through a pipe. Measured in Volts (V).
- current: The rate of flow of electrical charges. Think of it as the diameter of a pipe with flowing water, the wider the pipe the more water that will flow through it. Measured in Amperes(A).
- Resistance: The ability of a material to hinder the flow of charge(current). Thnk of it as sand in a pipe that prevents the flow of water in it. Measured in Ohms (Ω).
These basic concepts will be repeated all along the lessons because without them, then we can not talk about electricity at all.
- Anode: The electrode or wire through which current enters a device, such as an LED, where current can flow only in one direction
- Breadboard: A device used for prototyping electronic circuits that allows for easy connection of electronic components
- Cathode: The electrode or wire through which current exits a device, such as an LED, where current can flow only in one direction
- Circuit: A conductive path that electric current can flow through
- Conductor: A material that allows electrons to easily pass through it
- Conductance: A measure of how well a material allows electrons or electrical current to flow through it; measured in siemens
- Current: A measure of the number of electrons (or amount of charge) passing through a point in a circuit in a specific time; measured in amperes (amps)
- Electron: A part of an atom that is negatively charged and can be passed from atom to atom, creating a flow of electricity
- Insulator: A material that resists the flow of electrons
- Ohm’s law: A scientific law that states that voltage is directly proportional to current V = I • R
- Prototype: An initial model of a device that can be used for testing and modification from which the final product is developed
- Resistance: A measure of the opposition to the flow of electrons through a material; measured in ohms
- Resistor: An electronic component that reduces the current in a circuit
- Voltage: A measure of the difference in electrical energy between two points; measured in volts
Electricity can be thought of as the flow of electrons through a conductive path. One way to measure electricity is by electric current. The current in a river is the amount of water flowing past a certain point in the river over a certain time. In the same way, electric current is the number of electrons flowing through a certain section of a conductive path in a certain time. Current is measured in amperes, or amps for short. One amp is equal to about 6,241,500,000,000,000,000 electrons flowing past a point in one second.
Another common electrical measurement is voltage. Voltage is a difference in electrical energy between two points. It is a comparison of the number of electrons at one place versus another. One way you can think of voltage is as pressure that pushes electrons through a circuit – the more electrons, the more pressure and the more voltage. The unit for measuring voltage is the volt. A standard AA battery has a voltage of 1.5 volts between its two ends. A standard wall outlet has a voltage of about 120 volts in the United States and 220 volts in most European, Asian, and African countries.
Resistance is another common electrical measurement. Resistance is just what it sounds like – a measure of how a material resists the flow of electrons. Good insulators such as plastic, rubber, and glass have very high resistance, slowing the flow of electrons. Good conductors such as metal have very low resistance and allow electrons to easily flow. Resistance is measured in ohms. The Greek symbol omega (Ω) is often used to symbolize resistance in ohms.
Conductance is a measure of how well a material allows electricity to flow through it. It is the opposite of resistance. If a material has a high conductance, it has a low resistance. Materials that have a high resistance have a low conductance. This is called an inverse relationship. Conductance is measured in siemens (S).
Note: In the past, the unit for measuring conductance was the mho – ohm spelled backward. The mho was an indication of the inverse relationship between conductance and resistance, measured in ohms.
Georg Simon Ohm is credited with discovering the relationship between voltage, current, and resistance. In a paper he published in 1827, he wrote about how the current in a circuit is proportional to the voltage pushing the electrons through the circuit. This discovery is called Ohm’s law and can be written in the form:
VOLTAGE = CURRENT • RESISTANCE or V = I • R
Note: Variables are letters or symbols that represent a certain quantity in an equation. For Ohm’s Law, V is used to represent voltage. The letter I is used to represent current. For resistance, the letter R is used.
Using algebra, you can rearrange this equation to solve for current or resistance:
CURRENT = VOLTAGE/ RESISTANCE or I = V/R RESISTANCE = VOLTAGE/ CURRENT or R = V/I
Resistors usually have two wire leads, one in each end. Electricity can flow either direction through a resistor, which means that resistors can face either direction in a circuit.
A resistor is an electrical component that resists the flow of electrons and helps control the amount of current flowing through the circuit. Resistors work by converting certain amounts of electrical energy to heat by creating resistance in the circuit.
Resistors usually have two wire leads, one in each end. Electricity can flow either direction through a resistor, which means that resistors can face either direction in a circuit.
The value of a resistor indicates how much resistance will be added to the circuit. Recall that resistance is measured in ohms. A 220-ohm resistor will add 220 ohms of resistance to the circuit. A 10-megohm (10 MΩ) resistor will add 10,000,000 ohms of resistance to a circuit.The table here shows some of the common prefixes used in electrical measurements as well as their values.
Prefix | Amount | Word | Examples
------------|-------------------|-------------------|----------------
Pico | 0.000000000001 | trillionth | picofarad
nano | 0.000000001 | billionth | nanofarad
micro | 0.000001 | millionth | microohm,microamp,micrfarad
milli | 0.001 | thousandth | milliamp, millivolt
kilo | 1,000 | thousand | Kilovolt, Kiloamp, Kiloohms
mega | 1,000,000 | million | megaohm, megawatt
Notice the color bands on your resistor. Resistors are usually marked with either four or five color bands. These bands indicate resistance. Each color represents a different value.
Color | Digit | Multiplier | Tolerance (10%)
------------|-------------------|-----------------------|-----------------------
Black | 0 | 10^0(1) |
Brown | 1 | 10^1 | 1
Red | 2 | 10^2 | 2
Orange | 3 | 10^3 |
Yellow | 4 | 10^4 |
Green | 5 | 10^5 | 0.5
Blue | 6 | 10^6 | 0.25
Virgin | 7 | 10^7 | 0.1
Grey | 8 | 10^8 |
White | 9 | 10^9 |
Gold | | 10^-1 | 5
Silver | | 106-2 | 10
The table above indicates what each color represents. Notice that the multiplier is written in scientific notation. The exponent shows how many zeros to add after the digits from the other bands. For example, the 4-band resistor shown at the top of the chart starts with a brown band. Brown has a value of 1, so the resistor’s value starts with 1. The second digit is black, so the next digit is 0. The multiplier band is orange, which has a value of 3. This means we add three 0s. This gives a total resistance of 10,000 ohms, or 10 kilohms (10 kΩ).
Note: A resistor is considered a non-polarized component. That means it doesn’t matter which way the resistor faces in the circuit.
- Open circuit means the wires are cut off so there will be no current flow, but there is voltage.
- Closed circuit means the wires are connected so there will be flow of current, but there is no voltage.
- Short circuit also refers closed circuit. The terminals are forced to have zero voltage potential.
Components in a circuit can be wired in one of two ways, series or parallel.
- In a series circuit, the components are wired one after the other, forming a single path for current to flow through.
- In a parallel circuit, components are wired in such a way that there are multiple paths for electricity to flow through.
You can check the image library to see how a seris and parallel circuit look like.
In this lesson, you’ll write programs to control the LEDs in the circuit, including a program for a traffic light. With the traffic light program complete and running, you’ll use a multimeter to take electrical measurements of the circuit.
Circuit diagram and sketch file can be found in the traffic light folder.
- Arduino Uno Board
- Breadboard
- LEDs (Red,Yellow & Green)
- Jumper Wires
- 3x 220ohms Resistor
- USB Cable
The sketch can be found in same folder.
At many busy intersections, traffic lights have pedestrian buttons that people walking on the sidewalk can press. This lets the traffic light know that people, not just cars, need to cross the street. In this activity, you’ll add a pedestrian button to your circuit. You’ll then program the traffic light to function differently when the button is pressed.
Circuit diagram and sketch file can be found in the traffic light with pedestrian folder.
- Arduino Uno Board
- Breadboard
- LEDs (Red,Yellow & Green)
- Jumper Wires
- 3x 220 ohms Resistor
- 1x 10k ohms Resistor
- Push Button
- USB Cable
In many homes and office buildings, the lights are controlled by a dimmer knob that enables you to dim the lights to a setting that is comfortable for the environment. In this lesson, you’ll investigate analog signals and how they can be used to control a circuit. You’ll create an LED circuit that dims the LEDs when you turn a device called a potentiometer.
A potentiometer is a type of variable resistor. In other words, it can be changed to have no resistance or to have a great deal of resistance. The potentiometer we will using has a range of 0 to 10,000 ohms.
Inside a potentiometer is a resistive material and wiper that slides along this material. Each end of the resistive material is connected to a pin or terminal. These would be Pins A and B. The resistance between Pins A and B is fixed and is the maximum amount of resistance a potentiometer can add to the circuit. The potentiometer used here has maximum resistance of 10 kilohms.
A third pin is connected to a wiper. The resistance through the wiper, or Pin C, depends on the position of the wiper as it contacts the resistive material. The more of the resistive material the current must pass through before exiting the potentiometer through the wiper, the higher the resistance through Pin C.
So, potentiometers change the resistance in the circuit. However, microcontrollers don’t read resistance; they read voltage. In the traffic ligh circuit, you used a digital pin to read the voltage as either HIGH or LOW. So, how do you get a potentiometer to affect the voltage in a circuit? By connecting the potentiometer to a power source and to ground. The wiper pin is usually connected to an analog pin on the Arduino UNO Rev3 board.
Circuit diagram and sketch file can be found in the Dimmer folder.
- Arduino Uno Board
- Breadboard
- LEDs (Red,Yellow & Green)
- Jumper Wires
- 3x 220 ohms Resistor
- Potentiometer
- USB Cable
In this lesson, we learn how to program and control our servo motor. You will also learn how to use capacitors to store charges and how to use external arduino library such as Servo library to control the servo motor.
A capacitor is an electrical component that stores an electrical charge like a battery. However, capacitors store charge in a much different way than batteries do. Batteries use a chemical reaction to produce electrons on one terminal and absorb electrons on the other terminal. Capacitors don’t produce electrons like batteries do. Capacitors are storage units where electrons are stored and released through the same terminal they came in.
Capacitors have two terminals. Some capacitors, like the ones we will be using are polarized. They have an anode and a cathode. With polarized capacitors, electrons flow in only one direction. Therefore, polarized capacitors are generally used in DC applications where current flows in one direction. Non-polarized capacitors allow electrons to flow in either direction. This makes them great for AC applications where current alternates directions. However, they can also be used in DC circuits.
Note: For polarized capacitors, the cathodes usually have a shorter wire and are usually marked with an arrow, a stripe, or a negative sign
Inside a capacitor, the terminals are connected to conductive metal plates that are separated by an insulator. The insulator that separates the plates is called a dielectric and can be made from ceramic, porcelain, glass, and even air. The dielectric material is what gives capacitors a wide range of types and uses.
In a way, you can think of a lightning storm like a capacitor. The clouds are one conductive plate, and the ground is the other. They are separated by the air, which acts as the dielectric. When enough charge builds up in the clouds, lightning jumps the air gap between the clouds and the ground and discharges the capacitor.
Lightning leads to a big difference between batteries and capacitors. Capacitors can discharge all their stored electrons very quickly whereas batteries discharge slowly. This makes the potential uses for batteries and capacitors much different. Batteries are good at supplying current over time, while capacitors are good at managing quick changes in current.
Capacitance is a measure of how much charge a capacitor can collect and store. It is measured in units called farads, named after Michael Faraday. Generally, the larger a capacitor’s physical size, the more capacitance it has. For example, a one-farad capacitor would be pretty large – perhaps the size of a two-liter bottle of soda. It could hold enough charge to potentially electrocute you. The capacitors you’ll use are in the microfarad range. That’s one-millionth of a farad. These capacitors hold far less charge and are much safer to work with.
Circuit diagram and sketch file can be found in the Servo folder.
- Arduino Uno Board
- Breadboard
- Capacitor 10micro Farad.
- Jumper Wires
- Servo Motor
- Potentiometer (10kOhms)
- USB Cable