Rosie is building an electromagnet. She has set her electromagnet up with an aluminium core, a wire wrapped around the core ten times, a 6 volt power pack, an ammeter, and a variable resistor. Explain to Rosie how she could test the effectiveness of her magnet and improve its design.

Expert Answers

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Rosie can test her electromagnet's effectiveness by doing an experiment in which she varies one aspect of her magnet at a time. The ammeter will tell her if she is successfully running electricity through her system. If she is running an experiment to see how to increase the magnet's strength she will need a quantity of small, identical metallic objects that the magnet will attract. A box of the same-sized paperclips would work for a small electromagnet of the type you describe. She can then test the magnet as she has it set up initially, and record how many paperclips it will lift off the table. Rosie should then change one part of her magnet at a time to see what will increase or decrease its strength as determined by the number of paperclips she can lift with it. Rosie can

  • change the type of core around which she has wrapped the wire.
  • increase/decrease the number of times she has wound the wire around her core.
  • increase/decrease the voltage of her battery, or add batteries.
  • change the resistance in her circuit by changing the setting on her variable resistor.

Rosie needs to record her data, and to be sure to only change one aspect of her magnet at a time, as this will be her independent variable for each experiment. The number of paperclips lifted is her dependent variable.

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