Classroom experiments and activities

Simple model of a generator

Build a simple generator using easily available material

  polish flagGrzegorz F. Wojewoda

I liceum Ogólnokształcące

Very often students have difficulty with understanding the phenomena associated with electro-magnetic induction. At the same time current flowing in home power supply network system is inductive current. In order to help students better understand the physical basis of operation of generators in power plants, I propose building a simple generator model with spinning magnet.

needed material

finished generator
  Material needed for the experiment
 The completed generator

1. Needed background

Middle School

    Core curriculum: Electromagnetic induction phenomenon
    Lesson Subject: Generation and transmission of electricity

Upper Secondary School

    Core curriculum: Electromagnetic induction
    Lesson Subject: Generator.

2. Needed materials
The following will be needed to carry out the experiment:

➢ two neodymium magnets,

➢ approx 100m long enamelled copper wire,

➢ light-emitting diode,

➢ empty bottle of milk (or similar),

➢ barbecue stick,

➢ insulating tape, 

➢ soldering iron,

➢ knife

➢ two-component Epoxy glue (poxipol)

needed material
    Fig 1. Material needed for the experiment

 2. Implementation

You can buy the neodymium magnets necessary for the implementation of the generator model from an online shop. All that is needed in order to find such a shop is entering "neodymium magnets" in a web-search engine, then select a shop from the resulting list. In a similar way, one can buy copper wire, or go to the nearest shop selling electronic parts, where one can also buy luminescent di-odes.
The cost of these materials should not exceed 10 €.
The empty milk bottle should be washed and stripped of covering containing the name and manufacturer of the drink. We begin by preparing the bottle to act as a generator stator. For this purpose, using a barbecue stick, we pierce the sidewall of the bottle, at the middle of its height. We have to make sure the puncture is along the diameter.
milk bottle
Fig. 2. Piercing the sidewalls of the bottle.

Then, using a knife, make cuts connecting the top edge of the bottle to the previously made holes.

cutting the bottle
   Fig. 3. Making cuts along the bottle sidewalls.
Next step is to build the generator rotor : the neodymium magnets should be fastened to the barbecue stick. When we put the barbecue stick between the two magnets, it will be pressed by the forces of attraction and, in principle, this should suffice. If we want the stick to be permanently placed between the magnets, the resulting gap should be filled with an adhesive, such as two-component epoxy glue (poxipol type).
magnets on barbecue stick
Fig. 4 Fastening neodymium magnets to barbecue stick

After the glue has dried, put the rotor in the stator. Put the rotor in the previously prepared holes through the cuts in the bottle sidewalls. 

motor in the bottle
  Fig. 5 Inserting motor into the bottle

Then, using several turns of an insulating tape, secure the rotor to prevent slipping. The rotor magnets should be placed exactly in the middle of the bottle.

securing rotor
   Fig. 6 Securing the rotor against slipping

To increase the stability of the generator stator, fasten the bottle side-walls with insulating tape. 

reinforcing rotor
  Fig. 7 Reinforcing bottle side-walls with insulating tape

Next, wind-up the stator windings. During the winding of copper wire, take care not to break the enamel layer. The ends of the windings wires should be near the top edge of the bottle. Make about 200 turns. 

 Fig. 8 Winding of generator windings

After having winded-up the windings, fasten the diode to the bottle.

Through two small holes, cut the diode filaments with a sharp knife blade. Diode filaments should not come in contact with each other.  

led on the bottle
Fig. 9 Attaching the LED to the bottle

Solder diode tips to windings wires .

soldering the diode
Fig. 10 Soldering diodes to windings wire

Cover the windings and soldering points using insulating tape : the simple generator model is ready for use. The pleasure of explaining why the LED, during generator operation, does not give a continuous but a flashing light should be left to the students. 

finished generator
Fig. 11 Ready generator model


And here you can see how it works: