Energy Is Energy
Product Management Coordinator for Physical Science
The Law of Conservation of Energy states that energy can neither be created nor destroyed, but it can be converted from one form to another. This is a big idea in science. It is covered in every science course, from biology to physics to environmental science. This is one of the concepts that all science teachers want to make sure students fully understand. The idea of energy conversion is covered in the Next Generation Science Standards (NGSS):
NGSS HS-PS-3: “Design, build, and refine a device that works within given constraints to convert one form of energy into another form of energy.”
This quick activity is designed to drive home the idea that the energy we use has to come from somewhere, and even though one form of energy may seem different from another form, it really is all the same. Energy is energy.
- Hand-Powered Generator
- DC Motor (3 to 6 V)
- 3 Miniature Lamp Sockets
- 3 Miniature Lamps (1.5 V, 0.3 A)
- 2 Alligator Clips
- Knife Switch, Single Pole-Single Throw
Follow the instructions for this activity closely and abide by established laboratory safety practices, including the use of appropriate personal protective equipment (PPE) such as gloves, chemical splash goggles, and lab coats or aprons. Do not eat, drink, or chew gum while performing the lab, and wash your hands before and after performing the activity. Connecting wires to batteries for a long time can cause the wires to heat, and the battery could leak or start a fire. Make sure to only connect the circuits described in this activity for a few seconds.
- Obtain all needed materials. Test the lamps and generator to ensure all the parts are in working order. Place 3 lamp bulbs in 3 lamp sockets.
- Connect the 3 lamp sockets in series with the switch, using the alligator clip leads. Connect the hand-powered generator to the terminal leads, completing the circuit.
- Close the switch and have 1 student turn the handle of the hand-powered generator at a sustained speed sufficient to light the 3 lamps. Have a second student open the switch. The student turning the handle should describe the difference in turning the handle when the lights are connected and disconnected.
- Have the first student continue turning and have the second student close the switch, completing the circuit. Again, have the student turning the handle describe any change.
- Disconnect the generator from the miniature lamps, and connect the hand-powered generator to the terminals on the DC motor where a battery or power supply would normally be connected.
- Begin to spin the handle of the generator. The coil of the DC motor should begin to rotate, as if a battery were being used. It may be necessary to give the coil a small push to get the motor started.
- Observe the amount of force required to turn the handle. Have a second student open the switch, breaking the circuit.
- The student turning the handle should notice a change in the amount of force required to turn the handle.
- Continue turning the handle and have the second student reconnect the circuit by closing the switch. Again, the coil may need a push to get started.
When there is a load on the generator, the generator handle is more difficult to turn. Without a load, the handle is easier to turn. This directly demonstrates that the mechanical energy being put into the system by the person turning the handle is being converted to electrical energy by the generator. The faster you turn the handle, the brighter the lights shine or the faster the motor turns.
Here are some products that can be used for this activity.