Similarities between magnetic fields and electric fields:
- Electric fields are produced by two kinds of charges, positive and negative. Magnetic fields are associated with two magnetic poles, north and south, although they are also produced by charges (but moving charges).
- Like poles repel; unlike poles attract
- Electric field points in the direction of the force experienced by a positive charge. Magnetic field points in the direction of the force experienced by a north pole.
Differences between magnetic fields and electric fields:
- Positive and negative charges can exist separately. North and south poles always come together. Single magnetic poles, known as magnetic monopoles, have been proposed theoretically, but a magnetic monopole has never been observed.
- Electric field lines have definite starting and ending points. Magnetic field lines are continuous loops. Outside a magnet the field is directed from the north pole to the south pole. Inside a magnet the field runs from south to north.
The symbol used for magnetic field is B. The unit is the tesla (T).
The north pole of a compass points toward a magnetic south pole and away from a magnetic north pole. In that case, why does a compass point north on the Earth? The Earth's magnetic south pole is located near the geographic north pole, while the magnetic north pole is near the geographic south pole. This is not always the case. Every 100,000 years or so the magnetic field of the Earth reverses direction (that takes a couple of 1000 years or so).