in this article
Electricity, Electric Currents and Electrons
While we all know electricity is the energy that powers the lights and appliances in our homes, but what is electricity really? Essentially, electricity is made of subatomic particles called electrons that move around the electrical circuit, interacting with its various components. These electrons always flow in a full or complete circuit and need to get back to where they started, for example at the battery.
Conductors vs. Insulators
Electricity in the form of electrons can move through some material more readily than other material. The wires that connect mains electricity to a mains appliance is typically made of copper because copper is highly conductive, allowing electrons to pass through it very easily. The copper wire is coated with plastic to prevent accidental electrocution from touching the wire, as plastic is an insulator and does not allow electrons to pass through it.
Materials which allow electrons to pass easily through them are called conductors whereas materials that prevent electrons from flowing are called insulators. These properties allow us control over where electricity is allowed to pass and not to pass, and allows us to turn electronics on and off. Insulating properties of materials vary depending on what the material is and its thickness so it is important to make sure an appropriate insulator is used when handling electricity particularly with mains electricity.
Some common electrical conductors include: copper wire, metals, tap water, rain water and people. Common insulators include: the majority of plastics, dry wood, glass, ceramics and air. The impurities in tap and rain water make them conductors whereas pure distilled water is an insulator. Never operate live electrical equipment near a body of water outside or in the rain unless the appliance is designed specifically to be used outside in such conditions. Semi-conductor materials have properties which can change between being an insulator and a conductor under different conditions.
A complete circuit is required for any electronic circuit to work. A complete circuit is where a connection of connecting conductive materials goes in a circle from one battery terminal through equipment then back to the other batter terminal . If there is a spot in the circuit where the connection has a gap, the circuit will not work as air is bad conductor.
Gaps in a circuit are useful though when used at a switch to turn the circuit on and off. When the switch is off, or in the open position, it makes a break in the closed circuit which turns off the electricity to the appliance . When the switch closes the two metal contacts inside the switch join to complete the circuit, thus turning on the appliance.
There is a strong risk or death by electrocution if mains voltage electricity passes through a person’s body, as mains voltage electricity is very dangerous. If electricity is not properly cabled there could also be the risk of fire or explosion. As such, precautions must be taken when using any type of electricity but especially mains.
The most prominent risk of electrical shock is from contact with a live circuit. This occurs when an electric current flows through a person (as a conductor) which can cause the person’s hart to stop beating as a result (cardiac arrest).
Typically one is safe from electrocution from most electrical circuits that run off of domestic batteries, including 12 volt car batteries. Some power outputs around the home, however such as those from a uninterruptible power supply (UPS) for a computer or those from solar panels.
Isolating Mains Voltages and Checking Energy Supply
Most electrical appliances are equipped with a plug that is easy to disconnect from the wall to terminate the power supply. Home wiring, however, is not always as easy when the mains electricity is connected directly in the equipment such as in a burglar alarm. When this is the case, a switch on the wall or a fuse should be located and turned off so as to cut power to the appliance prior to a person working on it.
When working on equipment that is wired into the mains it is important to ensure that the mains power supply is disconnected before working on the equipment so as to avoid electric shock. A home voltage detector can be used (after following the above steps for disconnecting power) to test if the power was successfully isolated. The home voltage detector often resembles a plastic pencil with a white tip. When the tip is placed near a mains voltage, the tip will light up red or beep (or both) to indicate that the wire is “live” or has a current running through it.
Before beginning to work on mains voltage it is important to seek the help of another person, or at the very least have another person close by in the event of an emergency. If a person is electrocuted and is still connected to the electrical supply, do not touch them in an effort to move them away from the electrical source, as the electricity would jump from that person’s body to your own. When possible, disconnect the electrical power supply by unplugging or turning off the switch instead. If disconnecting the power supply is not possible, use an insulator (such as a wooden or plastic boom handle) to push the person away from the power supply, and promptly dial for an ambulance.
For more information on electrical circuits and electrical safety, consider the following resources:
- Electric Circuits
- Explaining How Electric Circuits Work (PDF)
- Electricity Teaching Resources
- Electric Circuits Lesson Plan
- Endeavor Energy’s Electric Kids
- “Playing with Electricity: Exploring Electric Circuits Through Open Ended Play” (DOC)
- A Complete Circuit Unit Plan (PDF)
- “It’s Electric! A Web Quest about Electricity”
- Electric Circuits (with schematics)
- How Do Batteries Work?