Find out whether you can power a light using wireless electricity!
Time: approximately 30-60 minutes.
- AA battery
- battery holder with positive and negative wire leads
- thin magnet wire (insulated wire)
- LED bulb
- breadboard (optional)
- Transistor (PNP 2N2222A or similar)
- electrical tape
This experiment requires that you make 2 separate coils using insulated magnet wire. The coils are similar but not the same.
Make Coil #1
- Coil #1 will have two ends.
- Wrap a simple coil on a round object (about an inch in diameter) with 26 turns of wire.
- use electrical tape to keep the coil in place leaving excess wire for the two ends that will connect to the LED bulb
- scrape the coating off the two ends and wrap/connect to the LED bulb
Make Coil #2
- Coil #2 will have three ends.
- Using the same diameter object, make another coil and start with 13 turns.
- After the 13th turn, leave about 4 inches of excess wire and bend it back and make a twisted loop about two inches long (this will be the 3rd end of the coil).
- After you have made the twisted end, continue wrapping the coil with another 13 turns
- use electrical tape to keep the coil in place
- scrape the coating off the of the three ends (two ends of the coil plus the middle twisted end)
Putting it all together
- You can wire it on a simple breadboard as follows
- A transistor has 3 terminals. If you are using the same transistor we are using, face the flat side of the transistor towards you. The wires each have a name from left to right: emitter, base, collector
- Connect the emitter to the negative channel of the breadboard
- Connect the base to a5
- Connect the collector to b4
- Now Connect the 3 wires of coil #2 as follows
- Connect the twisted wire from coil to the positive channel of the breadboard
- Connect 2nd wire (should not matter which) to c4
- Connect the 3rd wire to c5
- Connect batter leads to appropriate positive and negative channels on the breadboard
- Hold coil 1 over coil 2 and move it farther and closer to coil 2
- What happens when you pass coil #1 over coil #2?
- What happens when you move them closer and farther away?
- What do you think is happening?
When electricity passes through a wire, a magnetic field is generated. Coiling the wire can magnify the strength of the magnetic field. When a coil of wire passes through a magnetic field, electrical current can flow through the wires of the coil. A magnetic field can be be generated by a magnet or by another coil of wire with electricity passing through it. In order for this experiment to work, the source of magnetic field must be turned off and on quickly b/c it is the change in magnetic field that induces an electrical current through the wire. To facilitate this change in magnetic field, we use a transistor which is designed to cycle on and off frequently. This change in magnetic field of coil #2 induces a current through the wires of coil #1 and provides enough current and voltage to power the LED. You may have seen wireless charger adapters are Starbucks or in other settings. The principle is the same.
- Experiment with more windings in each coil or change the number of windings in coil #1 and coil #2.
- Experiment with distance between the coils.
- more turns should reduce heating up of the coil