The current produced by sources of electricity comes in two main forms: direct current (DC) and alternating current (AC). If no voltage exists, a current will not flow and work cannot be done. The higher the voltage, the more work an electric current can do. It is helpful to remember that a current is a flow of electrons and electrons have mass (therefore current is a mass of flowing electrons!). If no height exists, the water will not flow and it will not have any energy due to motion.Ī voltage (similar to height) is needed to cause an electric current to flow (think of cascading water) so that it can deliver energy to an electrical device or appliance. The greater the height of the waterfall, the more energy the water has when it reaches the bottom. A height is needed for the water to flow down the waterfall. The relationship between voltage and electric current is similar to the relationship between the height of a waterfall and the water that flows down it. The Relationship between Voltage and Current An ampere is defined as having one coulomb (6.25 x 10 18) electrons flow past a point in an electric circuit every second. The unit of current is the ampere, or amp. In a circuit, current delivers energy from a source of electricity to an electrical device (e.g. CurrentĮlectric current is simply the flow of electrons (or, in some cases, positive charges). One volt is defined as doing one joule (0.74 foot-pounds) of work to move one coulomb (6.25 x 10 18) electrons. Only then will the battery actually do work. However, the battery will not light the bulb unless it is connected to the bulb in an electric circuit. For instance, a battery that is sitting on a table but not connected to anything has a voltage, or the potential to do work such as lighting a light bulb. The potential to do work should not be confused with actually doing work. The greater the voltage, the more potential the electricity source has to do work. illuminate light bulbs, run electrical appliances). Volts, Amps, and Watts: What are they? VoltageĪll sources of electricity, such as batteries or generators, have the potential to do work (e.g. If the microwave oven is used an average of a half hour each day, the average amount of energy is uses per day isĦ00 watts x 0.5 hours per day = 300 watt-hours per day Using the information on the microwave label, the wattage is equal to Voltage x Current = Wattage. If the voltage and current are listed on an appliance but the wattage is not, the wattage can be calculated by multiplying the voltage by the current. The wattage of the microwave is 600 watts. The 60 HZ number means that the current alternates at a rate of 60 times per second. The information on the label tells us that the microwave oven needs 120 volts of electricity in the form of alternating current (AC) to operate, and draws 5 amps (amperes) of current during its use. X-15Z 120 Volts AC 5 A 600 Watts 60 HZ Made in USA For example, a label on a microwave oven may look like this:ĪCME, Microwave Oven Model No. Wattage and other electrical information is often listed directly on the appliance or equipment. The relationship between the wattage, time of use, and the energy used by an appliance or piece of equipment can be expressed by this formula: Wattage (Power) x Time = Energy Useīy using this formula, we can compare the energy used by electrical appliances and equipment to see which ones use the most electricity. For instance, a 1,200-watt microwave used for only 30 seconds uses less energy than a 600-watt microwave does in one-half hour. However, an appliance with a higher wattage will not use much energy if it is used for only a few seconds, whereas an appliance with a lower wattage may use a lot of energy if it is used for a number of hours. For example, a 1,200-watt microwave oven uses twice as much electrical energy and produces twice as much heat in one minute as a 600-watt microwave oven. The higher the wattage, the greater the amount of electrical energy that an electrical appliance or piece of equipment uses over a period of time. Electrical power is usually measured in watts hence, electrical power is often referred to as wattage. Power is the rate at which energy is used, or work is done, per unit of time. Power and time of use are the factors that determine how much energy is used by an electrical appliance or piece of equipment. Unit 4: Energy Through Our Lives-Part II Section F.
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