like iron, and this power of attraction is not limited to the magnet
itself but extends into the region around the magnet.

308. Magnetic Properties of an Electric Current. If a
current-bearing wire is really equivalent in its magnetic powers to a
magnet, it must possess all of the characteristics mentioned in the
preceding Section. We saw in Section 296 that a coiled wire through
which current was flowing would attract iron filings at the two ends
of the helix. That a coil through which current flows possesses the
characteristics _a_, _b_, _c_, and _d_ of a magnet is shown as follows:--

_a_, _b_. If a helix marked at one end with a red string is arranged so
that it is free to rotate and a strong current is sent through it,
the helix will immediately turn and face about until it points north
and south. If it is disturbed from this position, it will slowly swing
back until it occupies its characteristic north and south position.
The end to which the string is attached will persistently point either
north or south. If the current is sent through the coil in the
opposite direction, the two poles exchange positions and the helix
turns until the new north pole points north.

[Illustration: FIG. 226.--A helix through which current flows always
points north and south, if it is free to rotate.]

_c_. If a coil conducting a current is held near a suspended magnet,
one end of the helix will be found to attract the north pole of the
magnet, while the opposite end will be found to repel the north pole
of the magnet. In fact, the helix will be found to behave in every
way as a magnet, with a north pole at one end and a south pole at the
other. If the current is sent through the helix in the opposite