If a piece of lodestone is dipped into iron filings it is noticed that the filings cling in tufts, usually at two places in particular (Fig. 30.1). When the experiment is performed with a bar magnet the filings are seen to cling in tufts near the ends. Few, if any, filings are attracted to the middle of the bar.
The places in a magnet where the resultant attractive force appears to be concentrated are called the poles.