You're probably familiar with words like “volt” and “watt” from your everyday life. You put a new nine-volt battery in your smoke detector a couple of times a year, and you've probably replaced all the old 100-watt incandescent bulbs in your light fixtures with 25-watt CFLs. So, the words are familiar, but most people still have just a vague idea of their real meanings. Do volts kill? Is one watt deadly? A thousand watts? Is it important to know? Do you know?
At the risk of oversimplification, you can consider electrical current to be flowing electrons and talk about it like flowing water. Like water runs downhill, an electric current also runs down a kind of slope, except that the slope a current follows runs from a negative to a positive charge. Having a negative charge means that too many electrons are present; having a positive charge means that there's a shortage of electrons.
Voltage simply measures the difference in charges between two points. Think of voltage as the electrical “pressure,” like the water pressure in your plumbing. The greater the “pressure” –- the more difference in the charges at opposite ends of a circuit -- the higher the voltage in the circuit. Standard household current ("pressure") in the US is 120 volts; in the UK it's 220 volts.
A circuit's voltage has a constant value, for instance household current or a battery's rated output. The wattage a device draws as it performs is a constant, too; if there isn't sufficient wattage available, a device won't run or will perform poorly. Since both measures are constant, the variable factor in a circuit is its amperage. You can easily calculate a circuit's amperage: simply sum the watts drawn by all running devices and divide this number by the voltage.
If we return to the idea of electric current compared to water flowing through a pipe, the force at which water moves (water pressure) is similar to the voltage. If you wanted to fill both a bucket and a bathtub with water from the same pipe, the two containers' volumes are the equivalent of the wattage of different electrical devices. Let's say that you wanted to fill both and (for some reason) wanted both jobs to take the same amount of time. The pressure (equivalent to voltage) of your pipe is constant, so the water only needs to trickle to fill the bucket, but to fill a bathtub the water has to have much higher flow rates: the rate is the equivalent of amperage, the number of amps in the circuit.
Volts and Voltage
Volts get their name from the Italian physicist Alessandro Volta (1745-1827). Voltage measures “electric potential difference,” whatever that is. More questions: what's the difference between a AA battery and the current in your wall plugs?At the risk of oversimplification, you can consider electrical current to be flowing electrons and talk about it like flowing water. Like water runs downhill, an electric current also runs down a kind of slope, except that the slope a current follows runs from a negative to a positive charge. Having a negative charge means that too many electrons are present; having a positive charge means that there's a shortage of electrons.
Voltage simply measures the difference in charges between two points. Think of voltage as the electrical “pressure,” like the water pressure in your plumbing. The greater the “pressure” –- the more difference in the charges at opposite ends of a circuit -- the higher the voltage in the circuit. Standard household current ("pressure") in the US is 120 volts; in the UK it's 220 volts.
Watts That?
Watts are measure of electical power (like a car has horsepower); they're named for the Scottish engineer James Watt (1736-1819). Most electical devices work by converting electrical energy to heat, motion, or a combination of the two. Wattage (number of watts consumed) is the rate electrical devices like light bulbs, air conditioners and computers convert an electrical current to some other kind of energy. A 60-watt light bulb, for example, uses a constant 60 watts of electrical energy when turned on. Other devices consume variable amounts depending on how fast they run, etc.The Amp
Watts and volts are related to one another by a third quantity, called the ampere or amp. Amperes were named after a French physicist and mathematician, André-Marie Ampère (1775-1836). They measure the rate at which current flows through any spot in a circuit. Fuses or circuit breakers are rated in amperes; if the amount of current passing through a breaker (or fuse) exceeds its amperage rating, the fuse “blows” or the circuit-breaker “trips.” This is a safety measure: it prevents overheating in circuits to reduce the danger of fire. A circuit's amperage is the total watts drawn by all the running devices divided by the circuit's voltage: amps = watts / volts.A circuit's voltage has a constant value, for instance household current or a battery's rated output. The wattage a device draws as it performs is a constant, too; if there isn't sufficient wattage available, a device won't run or will perform poorly. Since both measures are constant, the variable factor in a circuit is its amperage. You can easily calculate a circuit's amperage: simply sum the watts drawn by all running devices and divide this number by the voltage.
If we return to the idea of electric current compared to water flowing through a pipe, the force at which water moves (water pressure) is similar to the voltage. If you wanted to fill both a bucket and a bathtub with water from the same pipe, the two containers' volumes are the equivalent of the wattage of different electrical devices. Let's say that you wanted to fill both and (for some reason) wanted both jobs to take the same amount of time. The pressure (equivalent to voltage) of your pipe is constant, so the water only needs to trickle to fill the bucket, but to fill a bathtub the water has to have much higher flow rates: the rate is the equivalent of amperage, the number of amps in the circuit.
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