Know Your Appliance; Voltage, Current and Resistance

The concepts of voltage, current and resistance are little-understood by most of the people who benefit from them, which is understandable considering how much faster science is moving than culture is, but is still strange and should probably be changed. If you’d like to better understand your electric appliances and how they work, here’s an article to help you brush up on the innerworkings of voltage, current, and resistance, and how they affect the way your stuff functions.

Electric current refers to the number of electrons in motion in a circuit. It’s measured in amps.

electric circuitsVoltage refers to the “pressure” that pushes electrons along through a circuit. As one would expect, the unit “volts” refers to the voltage of a current. If you live in the United States like I do, it’s likely that the power outlets in the wall of your house or apartment serve up 120 volts each.

Once you have these two terms down and know how many amps and volts are involved in a specific circuit, you can actually determine the exact amount of electricity consumed. This particular figure is generally measured in something called watt-hours or kilowatt-hours.The time-aspect of the unit may be somewhat unexpected, but its necessary part int he measurement becomes elucidated if you think about it in the following way:

Imagine that you own a space heater and it’s a cold winter day. You plug it into your wall outlet and measure the amount of current flowing from the wall outlet to the heater, which comes out to 10 amps. You can therefore deduce that it’s a 1,200-watt heater because that’s the amps (10) multiplied by the volts (120 [we assumed you were in the United States again]). This method holds true for any electrically powered appliance. If you have a light that draws only a third of an amp, you’ve got a 60-watt light bulb.

Ok but wait, what about the hour part? Right so let’s assume you’ve only got the space-heater plugged in and you’re checking out the power meter outside. The meter is there so that it can measure the amount of electricity flowing into your house and the power company can bill you for it. If your space heater is using 1.2 kilowatts and you leave it on for one hour, it will have used 1.2 kilowatt-hours of power. If your power company then charges you 10 cents per kilowatt-hour of power, the company will end up charging you 12 cents for every hour that your space heater is left on.

toaster2Now let’s cover resistance: Resistance is limit of how much electricity can travel through a wire at once and is measured in Ohms. According to Ohm’s law,

I (current) = V (voltage) / R (resistance).

Resistance sounds like a hindrance to the effort to use electrical appliances, but it’s actually a property that’s utilized all the time. For example, your toaster functions by sending wire through a wire that has high electrical resistance, forcing a lot of the energy of the moving electrons to be converted into heat while traveling through the wire. That heat turns your bread into toast.

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