Thursday, June 11, 2015
Electromagnets
A coil of wire is called a ‘solenoid’. A solenoid with a magnetic core is an 'electromagnet’.
We wound insulated copper wire round a steel nail, making 25 turns, and connected the ends to a power supply - 2 x 1.5V batteries. Our electromagnets could pick up 2 drawing pins. We investigated how to make them stronger. We found that increasing the number of turns off the wire, or increasing the voltage of the power supply, made the electromagnets stronger. The strongest could pick up 18 pins.
The steel nail is the core of the electromagnet. Ideally this would be made of iron, or another 'magnetically soft’ material, so that it was not magnetic when switched off.
To test how much difference the coil and the core made, we tried separating them. Our champion electromagnet could pick up 18 drawing pins, but when we removed the core and simply ran current through the wire, it couldn’t pick up any pins. The core alone, with no current, retained enough magnetism to pick up one or two pins. However, once reassembled, the electromagnet was much stronger. This demonstrates the purpose of the magnetic core of an electromagnet, which is to increase the strength of the overall magnetic field.
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