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In 1825 , William Sturgeon invented the electromagnet , with a single winding of uninsulated wire on a piece of varnished iron , which increased the magnetic force produced by electric current .
 William Sturgeon
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 William Sturgeon