Make an electromagnet to move a plunger, then use it to make a door bell and a launcher (electric catapult).


You have already made electromagnets with iron cores and examined their magnetic forces. In your experiments you wrapped the insulated wire right over the core; however, you could also wrap the wire on a plastic or paper tube and then insert the nail in the tube. The tube with wire on that will form the coil. The metal you insert in the tube will be the core. When the core is removable, you may also perform additional experiments related to electromagnet. For example you may try to find out how do different core materials (iron, copper, aluminum, air,...) affect the strength of your electromagnet. If you try such experiments, you may notice that the magnetic force pulls the core into the tube with a grate force. That is right. A core with partially inserted core will actually pull the core in when electricity is applied. An electromagnet with moving core is called solenoid. Solenoids are used in door bells and electrical valves and switches. Every washing machine has solenoids to open or close the valves or release detergents into the machine when needed. In this project you will make solenoids and use them as door chime and electric launcher (electric catapult).

Problem and Purpose:

Make an solenoid (electromagnet with moving plunger) and use it as a door chime and a launcher. 

  • 2" (or 5 cm) long plastic tube from a straw or a pen. A wooden straw may be used as well.
  • 40 feet (12 meters) magnet wire
  • Nail or iron rod that can slide in the tube.


  1. Get a 2" (5 cm) tube and wind 40 feet (12 meters) magnet wire around it in a way that about one foot (30 cm) wire remains unwind from each end.
  2. Wrap some masking tape on the wire to hold it in place and protect it from getting unwind. 
  3. Use a sand paper to remove the insulation from the ends of the wire where you make the connections.
  4. Connect one wire of the coil to the battery holder. 
  5. Connect the other wire of the coil to a switch you install on a board. Connect the other side of the switch to the remaining wire of the battery holder.
  6. Test your circuit by placing a compass near one end of the coil and pressing the key. Does compass must move? If not, check the connections.
  7. Insert about one inch (2 cm) of the nail inside the tube and push the switch. This will rapidly pull the nail into the tube. Now your solenoid (or magnetic plunger) is ready. You can use it to make many different things. 
When electricity is applied, the core (nail) is pulled into the coil. In most solenoids a spring will push back the core when electric current is stopped. In this way the action can be repeated. 

Make a door chime

Simple Chime:

When the nail is pulling inside and comes out of the other end, it may hit a spoon or any other metal object hanging from a string and create a sound.

Double Chime:

Use tape or any other method to mount your coil vertically on a wall or on the side of a box. Insert the plunger (nail) inside and then place metal bars on both ends of the coil. When you push the switch, the nail is pulled up and hit the upper bar. This creates the first sound. If you release the switch, the nail will fall back down and hit the lower metal bar causing the second sound. Metal bars can be any metal object that can make sound. You may use empty metal cans instead of metal bars.

Make an electric Catapult

Catapult is a device that can launch an object.  You can use your solenoid as an electric catapult. Hold your electromagnet at the edge of a table horizontally (Be careful not to aim anybody). Pull the plunger  back, insert a small pebble and close the switch. Experiment with the catapult to see at what angle the catapult will give you maximum launching distance. Also experiment with the size of the pebble or initial position of the nail.

Note: For best results, the inner diameter of tube must be slightly more than the diameter of the core (nail).

More Than 10 Projects in One Kit

The advanced and standard electromagnetism kits provide you with the opportunity of doing more than 10 different experiments and projects related to magnetism and electromagnetism. If you do not have the kit, please order it now.

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