People often use direct current as a means to charge batteries and their electronic devices. They also use DC power for third rail power systems and railway propulsion. While DC means direct current, it also means constant polarity. Some types of DC will have variances in their voltage, while most will not. A good example of varying voltage would be fluctuating voice signals on a power line. One should never try to reverse the polarity in a DC device, unless it features a diode bridge that will allow for the switch. Most of the battery-powered devices that people use do not have this bridge, so trying to alter the polarity would actually destroy the device.
The automotive industry and aircraft often use these types of systems. Most of the time, vehicles will use 12-volt power, although a select few may have 42-volt or 6-volt systems. Most light aircraft use 12-volt or 28-volt. Phone systems will often use both AC and DC components in them. Anything that contains a battery is running on DC power, from portable radios to toys.
Inventor Thomas Edison was a champion of DC power. He and others saw that electrical energy and magnetic fields had a close relationship. When there is a magnetic field near wires, it causes the electrons in the wire to flow in a single direction, which we've already established as being direct current. They flow because they are either attracted or repelled by the magnetic poles. This discovery showed scientists that it was possible to hold energy in a battery and then harness it.
However, DC was not the only source for electricity. Another scientist, Nikola Tesla, worked on the alternating current system because it was able to transfer power more efficiently, he thought. He did not make use of magnetism on the wire in a steady direction. Instead, the magnet rotated, offering alternating power. When the magnet was in a certain position, the electrons would flow in one direction. Changing, or alternating, the position of the magnet would change the way the electrons flowed.
One of the biggest differences in AC and DC is the amount of energy they can carry. DC voltage can produce a certain amount of constant electricity. The further it travels the weaker it becomes. AC voltage from generators can change their strength, increasing or decreasing it when they travel through transformers.
By using an adapter, it is possible to change AC energy to DC energy. This happens in many electronic devices, such as musical keyboards, laptop computers, and other devices that require adapters.
A DC-DC converter is a type of electronic circuit that takes the DC source and then converts it from the current voltage into another voltage. In some instances, one may have to increase or decrease the voltage. This is actually very common when it comes to automobiles. Some devices you might use in your vehicle, such as a portable DVD player for the kids, require a certain amount of power to run. Too much power and it could destroy the devices. Too little power and it would not run. Since the device needs to draw from the vehicle’s battery, and the battery might be too powerful, there needs to be a conversion of power. However, it needs to remain DC voltage. To accomplish this, a variety of different types of DC-DC converters is available.
The converters will actually take the power from the battery and cut it down to a usable level. In the cases of devices that might need more power, a converter can step up the power. Many of the devices that you use in the vehicle come with adapters that you can plug into the vehicle. The adapters will convert the power to ensure your device works appropriately. It is important to make sure you are always using the right adapter with the device though. Otherwise, it could be drawing too much power, which could seriously damage the electronics.