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Work and Energy

  • K2-40: MAGNETIC ACCELERATOR

    K2-40
    Demonstrate magnetic potential energy
    A slightly curved track holds a series of steel balls. One ball, superficially similar to the others, is a magnet. To use: Fill the track with nonmagnetic balls, and release a single ball from one upper end of the track. It rolls down and across the track until is collides with a stationary line of balls. As expected, the last ball in the line moves out with slightly less speed than the incoming ball. Now repeat the demonstration, replacing the first stationary ball in the line with the magnetic ball and the result is quite different. The attractive force of the magnet adds energy to the system, in a quite dramatic fashion.

    A similar effect can be seen with C7-19: Gaussian Gun
    K2

  • K4-05: MAGNETOELECTRIC GENERATOR WITH METERS AND LOADS

    K4-05
    An AC generator with rectifier, meters and several loads.
    The current vs. voltage relations can be observed for various loads using built-in meters. A bridge rectifier is used to feed a DC motor which lifts a 1 kg mass. An individual turning the generator crank can feel the effect of the load.

  • K4-07 BICYCLE GENERATOR

    K4-07
    Demonstrates a 110 VAC magnetoelectric generator, and the relationship of work to power output

    Pedaling the bicycle generates 110 VAC, which can be used to light an array of five 110 volt 150 watt lights. The sum, totaling 750 watts or about one horsepower when fully lit, can be verified using the voltmeter on the generator housing.
    K4, FS1

  • K4-09: BICYCLE GENERATOR - LIGHT BULBs VS CFLs

    K4-09
    Compare brightness and power requirements of regular tungsten filament light bulbs and compact fluorescent lamps.
    Pedaling the bicycle generates 110 VAC, which can be used to light an array of four 110 volt 60 watt incandescent light bulbs. The sum, totaling 240 watts when fully lit, can be verified using the voltmeter mounted on the bicycle. Alternatively, switch in the array of 15 watt CFLs (compact fluorescent lamps) and use the bicycle generator to light them. These CFLs are equivalent in light output to the 60 watt incandescent bulbs. It is easy to notice that the same amount of light created by the standard light bulbs can be created relatively easily using CFLs. The upper two photographs above show Krishna pumping the bicycle generator to light the incandescent bulbs (top photograph) and the CFL bulbs (second photograph); the lower two photographs show the arrays of lamps plugged into the 110 VAC outlet in front of the bicycle. The third photograph shows the incandescent bulbs and the last one shows the CFLs being activated. The student volunteer for riding the bicycle will testify as to the increased effort required to light the incandescents over the CFLs. This is a dramatic demonstration and can be used very effectively in class.
    K4, FS1

  • K6-22: ENERGY CONVERSION - IMMERSION HEATER

    K6-22
    Demonstrate quantitatively the conversion of electrical energy into heat.
    This 300-watt immersion heater is used to heat approximately 300 ml of water in a borosilicate beaker. Measure the initial water temperature with a digital thermometer, allow it to heat for a fixed time, then measure the final temperature. Compare the temperature change calculated for the energy conversion (as per Q=mcT where ! is the energy transferredm m is the mass of water, c is the specific heat, and T is the change in temperature) to that measured, and invite students to talk about the meaning of the difference (heat loss through the sides of the beaker, etc.).

    Note that the heater will (obviously) get hot! Do not allow it to burn your hand or the power cord.
    K6, I0