The cyclist's legs feel what the current meter shows - that four fluorescent bulbs can be lit with the same amount of power that it takes to light a single incandescent bulb. Mighty Motors Watching the current meter as they pedal, students see that when the fan is switched on, there is a brief surge as the motor starts. The current then settles to a lower, steady run value, which is pretty easy to pedal, and cyclists enjoy the cooling breeze. Switch off the fan and switch on the hair dryer.
Students are amazed at the effort needed for such a small amount of heat.
Some younger students are not strong enough to power even one compact fluorescent bulb, but they can charge the capacitor bank with short bursts of pedaling. This potential energy can then be converted back into kinetic energy, powering a radio for about 2 minutes, a tape player for 30 seconds, and a fluorescent bulb for 8 seconds. A British Thermal Unit is the amount of heat required to raise the temperature of one pound of water one degree Fahrenheit, but this doesn't have much meaning until you find yourself on the pedal-powering end of a beverage heater immersed in a pint of water. Even teenagers are good for only about 10 BTU, becoming too tired to maintain steady voltage after just a minute or two of pedaling. The resistance of an electrical wire or transmission cable is inversely proportional to the thickness of the conductor and directly proportional to its length.