SfC Home > Physics > Electricity > by Ron Kurtus (revised 13 February 2016) Homes in North America typically are powered with both 220-volt and 110-volt alternating current (AC) electricity. Modern outlets have three different shaped holes to assure plugs can only be inserted in one way. Two of the holes are considered grounds, for reasons of safety. Proper grounding and the use of fuses are important to maintain electrical safety in the home. Questions you may have include: This lesson will answer those questions. Useful tool: Units Conversion Typically, homes in North America receive 220 volts of AC electricity. Certain high-power devices, such as an electric stove, use the full 220 volts. The rest of the outlets in the house use 110 volts. Usually, three copper wires come into the home. Two are covered in black insulation and one has white insulation. Sometimes one wire is red instead of black. Each black or red wire is called a "hot" wire and has 110-volt AC.

The white wire is called the "common" and is grounded at the power station. Measuring across the two hot wires results in 220 volts. Measuring the voltage between a black (or red) and white wire, results in 110-volt AC. Copper wire is used because it is a good conductor of electricity. Materials that do not conduct electricity as good usually have a higher resistance. This results in wasted energy and the tendency to get hot, which could be a safety hazard. In the 1960s many electrical contractors started to use aluminum wire instead of copper. Aluminum is almost as good of a conductor as copper, but it is much less expensive. After a number of years, it was found that this type of wiring caused a potential fire hazard. Problems due to expansion caused overheating at connections between the wire and switches, outlets, or splices. Many homes had to be re-wired, although there still are many that still have aluminum wiring but have never had problems. The wall outlets usually have a one wide slot, one narrow slot and one round-with-flat-bottom hole.

This is to assure that each part of the plug will be used as it is supposed to and to increase safety. Older outlets have both slots the same size and no round hole.what's the best central ac unit The narrow slot is considered "hot" and is where the alternating current power comes out. home ac unit no powerThe wiring behind the outlet to this slot is usually black in the U.S. ac window unit installationThe wide slot is considered the "common" and is supposed to be grounded. Using the white wire as a common grounded wire, means that everyone is working from the same zero voltage position. The hole that is round on the top and flat on the bottom is an extra ground. Usually the wire behind the wall outlet has green insulation. Sometimes it is a bare wire.

This extra ground is to make sure your utensils are properly grounded in the situation that someone had improperly wired the house. It is an extra safety measure. Although the white wire is not supposed to be a "hot" wire, in some cases it is used that way, especially in older homes that have the old style outlets. In general, this is acceptable, but it can result in problems. If you touch a common wire that is properly grounded, you should not get a shock. But if that wiring has made it hot, you can get a shock. Also, by using the white wire where the black should be used, you may cause a short circuit. Proper grounding and the use of fuses are important for protection against shock, as well as to prevent electrical overheating and fire hazards Correct grounding is very important. Often ground wires are connected to water pipes that normally go into the ground. Connecting to a hot water pipe means that the water heater is between the connection and the ground. The water heater may have plastic parts that would insulate the connection to ground.

Thus, using a hot water pipe is not a good idea. Another consideration in using water pipes to ground the circuit is that plastic piping is often being used in plumbing. You must make sure there are no plastic pipes between your connection and the outside earth or ground. Fuses and circuit breakers are used as a safety measure in case of short circuits. A fuse or circuit breaker will break the connection if more current is passing through the wire than is considered safe. This will prevent the house wiring to overheat and start a fire. Most homes now use circuit breakers instead of fuses. One reason is because people with bad wiring in their homes that constantly blow out fuses, would then force pennies in the fuse receptacles, thus bypassing the requirement for a fuse. This removed the aggravation, as well as the expense of buying new fuses, but it also often resulted in serious electrical fires in the house. Most homes use both 220- and 110-volt AC electricity. Wires have black, red, white or green insulation, depending on their use.

The holes in modern outlets assure plugs can only be inserted in one way. Be curious about things you may take for granted Elements of AC Electricity - Basic electronics tutorial site DC and AC Electricity Resources Top-rated books on AC Home Wiring Basic Electricity by Bureau of Naval Personnel; (1970) $14.95 - Provides thorough coverage of the basic theory of electricity and its applications Do you have any questions, comments, or opinions on this subject? If so, send an email with your feedback. I will try to get back to you as soon as possible. Click on a button to bookmark or share this page through Twitter, Facebook, email, or other services: The Web address of this page is: Please include it as a link on your website or as a reference in your report, document, or thesis.Connecting the AC adapter Figure : Genuine HP part Figure : AC adapter components Tips for using the AC power adapter Use only the AC adapter provided with the computer, a replacement HP AC adapter, or a compatible AC adapter purchased

When connected to external AC power, the battery charge icon and the battery meter icon in the system tray changes appearance. When disconnected from external AC power, the computer uses power from the battery and the display brightness automatically dims to save battery life. To increase the display brightness, press + or reconnect the AC adapter. Figure : Battery charge icon Figure : Battery power meter icon Figure : Properly bundled adapter and power cords Figure : Improperly wrapped AC adapter cord Figure : Damaged AC adapter cord Understanding HP Smart Adapter messages This message does not indicate the AC adapter needs to be replaced or is defective. Use the appropriate AC adapter for your model notebook computer. Use the power adapter that came with your notebook computer for better performance. If you need a replacement adapter, see Ordering HP Certified Replacement Parts. Determining the AC power adapter wattage Figure : Example of a 65W AC power adapter label