The Alarm Clock that Never Wakes Me Up February 16, 2009
Posted by whereisphysics in Uncategorized.trackback
So while I was thinking about what I could write about for my physics blog this week, I just stared at my alarm clock at let time pass by. But then, I realized that I was staring at the perfect example for my blog this week. Since we just learned about DC circuits, I thought that my alarm clock must be an example for something we learned. Now, although I’m not 100% sure on how my clock is made, I think that the dimming switch on the alarm clock can be explained by the use of a variable resistor. As I slide the dial for the brightness of the display on my clock up and down, the intensity of the light emitted from my clock increases and decreases. One way of explaining this is that the dial that I am spinning is the control for the variable resistor, which basically looks like this:
| www.ngfl-cymru.org.uk The variable resistor works by changing the distance that the current must flow through a material with relatively high resistance. The reason why this resistor can change the brightness of the display is explained by the equations P=IΔV and P=I²R and ΔV=IR. We can use these equations to show that if the resistance of the resistor increases, than it will consume more of the power provided by the battery, leaving less power for the display to use (conservation of energy). If the power that the display uses is reduced, then it cannot give off as much light, resulting in a dimmer display.
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