Magnets. How do they work? How does the number of coils affect electromagnetism? Hypothesis: When there is a flow of moving electrons, a magnetic field is created. We use the equation F = NIlB (Force = Number of coils x Current x Length of Wire x Magnetic Field Strength) to work out the magnetic force produced in a wire when there is an electric current present. Using this equation we can see that increasing the length of the wire (amount of coils) gives a larger force. So increasing the amount of coils in an electromagnet gives a larger EMF. Variables-
Independent: Length of wire, Number of Coils in magnet Dependent: EMF produced, Magnetic Field Strength, amount of coils in magnet. Control: Volts, Amps, Ruler. AIM – To find out how the number of coils affects the magnetism of an electromagnet. BACKGROUND – Electromagnets use a fundamental force of physics, the electromagnetic force. Along with gravity and the strong and weak interactions (forces), the electromagnetic force is one of the four basic forces in the universe force. When a charged particle moves, it creates a magnetic field around its path of travel.
This magnetic field moves with the charged particle along its path. This magnetic field is one of the key components of the equation F = NIlB, arguably the most important equation involving electromagnetism. B stands for the Magnetic Field Strength, so using a bit of common sense you can see that changing B will change the overall EMF (electromagnetic force). I will Explain I and l in a minute (that’s L) We usually move electrons to do work, and when we move a lot of them, we create a large magnetic field around the conductor through which the electrons move.
The moving electrons are electricity, and if we coil the conductor through which the current is flowing, we can cause the magnetic field around the individual wires to “add up” and make one bigger field. The bigger field “reaches around” the entire coil of wire, and the magnetic lines of force all flow through the center, and then out one end, around the coil in all directions, and then back into the other end. This is where l (L) and N come into play, increasing the length of the wire and the amount of coils means or a stronger EMF just like with changing the Magnetic Field Strength. Different metals conduct differently; therefore some would be better for making magnets out of than others, a long side that is the fact that a large diameter should increase the Magnetic Field Strength as there is more mass of conductive material. It is important to use a direct current source because we want a “standing” magnetic field and not one that is constantly expanding and collapsing around our coil like it would if we use alternating current.
In AC, for each direction current flowed, a field would form, and then when the current changed direction, like it does in alternating current, that field would collapse and another one would form. This brings me to the last variable, I (even though it’s first in the equation) as you can probably guess, increasing the current flowing through the wire will increase the EMF as a larger current pushes more electrons through, creating more energy. EQUIPMENT – 2V Power Pack, wires with gator clips, ammeter, voltmeter, large amounts of wire to use as the coils (preferably copper), different metals to use as the base of the magnet (steel bolts, etc), pins, safety glasses, heat proof mat, rheostat. STEPS – Gather all stated ingredients. -Get the different metals and wrap them all with the same number of coils. -Connect the power pack, ammeter, volt meter and resistor. -Add one of the magnets into the circuit, put a pin at varying distances and record how strong the pull is. Lather rinse and repeat. -Once all magnets are done, try with a different amount of coils, then another amount. -Correlate the results in a table and use them to form graphs. BE CAREFUL OF: Hot wires, loose wires, short circuiting, water around the electrical equipment, Mr Lyon electrocuting you. RESULTS: Number of coils| Trial 1(cm)| Trial 2(cm)| Trial 3(cm)| Average| 20| -| -| -| -| 50| 1| 1. 5| 2| 1. 5| 74| 2. 5| 3| 3. 5| 3| 154| 5. 5| 6| 7| 6. 2|
The setting we used was 12Volts on the power pack, there was 5amps running through the circuit, and the resistance was at 2. 4ohms. Graph: There is quite an obvious trend here, when looking at the equation F= NILB and using the variables from the graph, we can see that as we increase the number of coils (N) F increases. B=F/NIL is the equation to work out the Magnetic Field Strength, by using the stats from the lab (I and L were kept the same) we can see that as F increases, so does B.
This means that the stronger the EMF (electromagnetic force), the stronger the Magnetic Field Strength is. So the higher B is, the stronger the pull on the pin. These results were pretty accurate, well pretty good for measurements by hand, but the magnets with small amounts of coils were impossible to work with by hand, as there was no way to tell what the force of attraction was like. We conducted 3trials as it was time effective and allowed for a good range of results that could be compared and such.
There were a number of sources of error in this experiment which included the resistance in the rheostat, the room temperature and the ruler. If I was to conduct this experiment again, I would look into more accurate ways to get the results as to minimize room for error. The error % for the ruler was….. (0. 5×0. 001/Measurement)x100 (1, 1. 5, 2, 2. 5, 3, 3. 5, 5. 5, 6, 7) 0. 001839×100 = 0. 1839% Error % for Voltmeter was…(0. 5×0. 2/12)x100 = 0. 83% Error % for Ammeter was…(0. 5×0. 1/5)x100 = 1% Add these together and we can see that the Absolute error % was 2. 01%