Investigating The Electromagnetic Force

A simple experiment to investigate electromagnetism by making a simple electromagnet.

This experiment involves making an electromagnet in order to see how big the magnetic force can be made using it.

First clamp a long iron nail upside-down (head of nail pointing downwards) using a wooden stand. Wind about fifty centimetres of insulated copper wire around the nail ensuring to wind it all in the same direction (though it doesn’t matter whether that’s clockwise or anticlockwise). This wire should be connected from the nail to a battery with a voltage of about three volts, a variable resistor (resistance up to 15Ω), through an ammeter and back to the other end of the coil around the nail, all in series.

It should be obvious that the lower the resistance the variable resistor is set to, the larger the current flowing through the circuit and the stronger the magnetic field strength around the nail.

An area worth investigation is the relationship between the height of the nail above a paper clip and the minimum current needed to magnetise it. After many different readings taken and each repeated at least three times, a graph should make the relationship between height and current a little clearer.

It is possible to calculate an exact value for the magnetic force caused by the coil. The paper clip should be stuck to the nail with a current large enough to support its weight. The current is lowered slowly until the minimum current needed to stick the paper clip is known. The mass of the paper clip should be found using an accurate balance. At the instant the clip drops from the nail, the force caused by the current is equal to the mass of the paper clip (in kilograms) multiplied by the gravitational field strength of the Earth (about 9.8 newtons per kilogram).

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