Electromagnets?

Question

I took apart a few electronic devices and I noticed that the electromagnet in them (or solonoid) had bare copper wire wrapped around an insulated metal. Are electromagnets more effective if the wire wrapped around isnt insulated? If so, does the core need to be insulated? If I had made an electromagnet using a stell nail and wire, the nail would become the magnet. Some electromagnets I have looked at have the metal part not just as the core, but also on the sides of the magnet, why?

Answer 1

It's worth noting that from your description the components you're talking about could be solenoids or inductors, depending upon what kind of device you took apart. However, they work similarly enough that for the purposes of your question the same principles apply.

It's unlikely that those wires are truly bare, as a bare wire can get shorted out which would at the very least would reduce the effectiveness of the solenoid or coil, and could cause bigger problems (i.e. fire).

There are usually two reasons to keep the insulation on a solenoid or inductor minimal. In the case of inductors, they're usually small and mass produced in large quantities, so the insulation is minimal largely for economic reasons (less insulating material makes the part cheaper). However, you do generally do want them insulated, because inductors are normally made with specific characteristics to accomplish a specific task, and a short would change the inductor's behavior and make it useless.

With something like a solenoid or an electromagnet, the reason to keep the insulation minimal is all about strength and power. With an electromagnet, the more electrons you get spinning around that nail, the stronger an electromagnet you have. There's two ways to do that. One way is to use more current (get the electrons moving faster). The other way is to wrap the nail with more loops of wire more tightly around the nail. By definition insulation is just material which doesn't conduct any current (that's its job afterall) which means that if you're trying to get more power by wrapping wire more tightly, after a certain point the insulation will actually get in the way.

Although solenoids and inductors are very different kinds of electronic parts, they both rely upon the principle of electromagnetic induction. A book on physics or electronics can give you more information on the subject if you're interested.

Answer 2

An electromagnet, in its simplest form, is a wire that has been coiled into one or more loops. This coil is known as a solenoid. When electric current flows along the coil, a magnetic field is generated around the coil. The orientation of this field can be determined via the right hand rule. The strength of the field is influenced by several factors. The number of loops determines the surface area of interaction, the amount of current determines the amount of activity, and the material in the core determines electrical resistance. The more loops of wire and the greater the current, the stronger the field will be.

If the coil of wire is empty in the center, it will tend to generate a very weak field. Different ferromagnetic or paramagnetic items can be placed in the center of the core with the effect of magnifying the magnetic field, for example an iron nail. In addition, soft iron is commonly used for this purpose. The addition of these types of materials can result in a several hundred- to thousand-fold increase of field strength.

At distances which are large compared to the magnet's dimension, the observed magnetic field obeys an inverse cube law. This means that the field strength is inversely proportional to the third power of the distance from the magnet.

In the case of an electromagnet in contact with a flat metal plate, the force needed to separate the two will be greatest if the two surfaces are machined as flat as possible. The flatter the surfaces, the more points of contact between them, and the smaller the magnetic circuit's reluctance to the magnetic field.

Electromagnets find uses in many places, ranging from particle accelerators, to electric motors, to junkyard cranes, to magnetic resonance imaging machines. There are also specialized applications that involve more than a simple magnetic dipole, such as the quadrupole magnets used to focus particle beams.

If enough electric current is passed through the coil of an electromagnet, the magnetic force between neighboring loops of wire can cause the electromagnet to be crushed by its own magnetic field.

Answer 3

Electricity flowing through a wire creates a magnetic field. By increasing the amount of wire and concentrating the magnetic field around a metal object, you can make a magnet. Materials: • a number 22 or 24 insulated bell wire (this works best, but any insulated wire will do) • a large iron nail • paper clips • a D cell battery • a partner Procedure: 1. Touch the nail to the paper clips. Notice that the nail does not attract the paper clips. 2. Wrap the wire tightly around the nail. Leave about 1/2 meter of wire free at both ends. 3. Place the paper clips in a pile on a table. 4. Hold the top of the nail and point the sharp end toward the paper clips. 5. Ask your partner to touch the wire ends to the two poles of the battery. (Do not hold the wires on the battery for more than 10 seconds to avoid draining the battery and causing the wire to overheat.) 6. At the same time, touch the end of the nail to the paper clips. Are you able to pick up paper clips now? Yes or No? 7. Ask your partner to remove one wire from the battery. What happens to the paper clips? a 9volt

Answer 4

The core doesn't need to be insulated.The electromagnets are more effective unwrapped.