To see how the number of coils on an electromagnet affect its strength.

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Title:

Electromagnet Investigation

Aim:

To see how the number of coils on an electromagnet affect its strength.

Scientific Knowledge:

     An electromagnet is a temporary magnet, meaning that it only goes and is in use, when you feel like it. Magnets have interesting properties. They can pull pieces of iron, cobalt or nickel towards them but not affect any other materials, even other metals such as copper or aluminium.

     When a magnet is freely suspended, it always comes to rest with the same pole facing north. This term is referred to as the ‘north pole’; the other is the ‘south pole’. If the north pole of a magnet is brought near to a south pole of a magnet, it will attract. However, if two poles are the same, they will repel meaning they will push away one another. This is where the saying is used, “Opposites attract.”

     All of these things happen because they have magnetic fields around them. This ‘field’ can be easily seen if iron filings are shaken around a magnet. If you place a bar magnet with iron filings surrounding them, you can observe that the filings will be going around towards their respective poles on the other side. When you place iron fillings round a coil or solenoid, you will notice that the magnetic field round the solenoid has the same shape as the field round the bar magnet. You will also notice that the field inside the solenoid will be very strong and uniform, which can magnetise things. The lines of force that shows the magnetic field, is called the lines of flux. The permanent magnets, unlike electromagnets, do have their advantages and also their disadvantages. Permanent magnets cannot be produced very large and more importantly, they cannot be switched off.

    A coil of copper wire will have no effect on a compass needle until an electric current is passed around it. When the process is complete, it acts and behaves just like a magnet, with poles and a magnetic field. Coils give a stronger magnet because the wire carrying the current has a magnetic field around it.

     An electromagnet is just a coil of wire with an iron core. When current flows through the wires of the solenoid it creates a magnetic field around it. So the soft iron core has the effect of increasing the magnetic field strength. The magnetic field around an electromagnet is just like the one round a bar magnet, only it can be made stronger. This means that the ends of the solenoid act like the North Pole and the South Pole of the bar magnet. Therefore, if the direction of the current is reversed the north and south poles will swap ends. If you look at one end of a solenoid, you can tell whether it is the north or the South Pole. The North Pole has the current shape going in an ‘N’ shaped way, and the South Pole has the current going in an ‘S’ shaped way. In an electromagnet, the same rules apply to every experiment. “The more turns of wires there are, the stronger the magnetic field, current and electromagnet”. However, bear that in mind, the flowing of electricity causes this effect, not the wire. This is mainly the reason for these devices to be called electromagnets, it an only work when switched on with coils. When and if the current is increased, the field becomes stronger; if it is reversed; and the current is switched off, the field will be lost.

     The scientific term for the word, ‘coils’, is solenoids. When the current flows, their external magnetic field, is just like that of a bar magnet. They also have the lines of forces running through their magnets. If an iron bar is placed inside the coil, the electromagnets become stronger because it concentrates the lines of magnetic force.

     A magnetic field is a region where magnetic materials such as iron or steel, and also wires carrying currents experience a force acting on them.

     Pure iron does not retain any magnetism when the current is switched off but a steel bar does. Generally, the pure iron is known to be magnetically ‘soft’, which are ideally used as cores for electromagnets. Because steel stays magnetic after being in a solenoid, it is magnetically ‘hard’. This means solenoids can be used to make permanent magnets made of steel.

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     So therefore, electromagnets can be made stronger by three factors that affect their strength. They are: a) increasing the number of coils: by increasing the coils, it allows more current to flow through efficiently making the process easier, b) increasing the current: by doing this, there will be more current thus making the electromagnet stronger and c) winding the coils around a ‘soft’ core: because by doing this, will make the electromagnet even better because the ‘soft’ iron is ideal for electromagnets. Also, electromagnets can obviously be switched off unlike normal magnets, which are permanent.

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