This gives the power in terms of only the current and the resistance. In a simple circuit such as a light bulb with a voltage applied to it, the resistance determines the current by Ohm’s law, so we can see that current as well as voltage must determine the power. Thus the two light bulbs in the photo can be considered as two different resistors. Incandescent light bulbs, such as the two shown in Figure 19.23, are essentially resistors that heat up when current flows through them and they get so hot that they emit visible and invisible light. This tells us that something other than voltage determines the power output of an electric circuit. Although both operate at the same voltage, the 60-W bulb emits more light intensity than the 25-W bulb. Let us compare a 25-W bulb with a 60-W bulb (see Figure 19.23). To get started, let’s think of light bulbs, which are often characterized in terms of their power ratings in watts.
In this section, we’ll learn not only what this means, but also what factors determine electric power. Power is the rate at which energy of any type is transferred electric power is the rate at which electric energy is transferred in a circuit. We also use electric power to start our cars, to run our computers, or to light our homes. Electric power transmission lines are visible examples of electricity providing power. Every day, we use electric power to run our modern appliances.
Power is associated by many people with electricity.
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