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What is the Difference Between Electric and Magnetic Fields?

Answer #1

Level 2 (suitable for students)
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Electric and magnetic fields differ in the following ways, for example:

  1. The unit of electric field is \( \frac{ \text{V} }{\text{m} } \) (volts per meter) and the unit of magnetic field is \( \frac{ \text{Vs} }{\text{m}^2 } \) (volts per square meter).

  2. Electric field \(\boldsymbol{E}\) is caused by both moving and non-moving electric charges. A magnetic field \(\boldsymbol{B}\), on the other hand, is caused ONLY by moving charges.

  3. A positive charge is the source of the electric field. In nature, a positive charge can occur as an electric monopole. In other words: Such a positive charge can occur alone. Magnetic fields, however, have no monopoles. That means: There is no single north pole (source), which generates the magnetic field. North pole (sources) and south pole (sinks) always occur together.

  4. Magnetic field lines are closed loops. Electric field lines, on the other hand, do not have to be closed, but can, for example, go 'to infinity', like the field lines of a point charge.

    Illustration : Magnetic field lines of a current-carrying coil form closed loops.
    Illustration : Electric field lines of a positive charge are not closed and are directed to infinity.
  5. When an electric charge moves in the electric field, the charge is accelerated. This causes the charge to change its energy. If, on the other hand, an electric charge moves through a magnetic field, the charge is NOT accelerated, that is, the charge does not change its energy. In short: E-fields do work on charges, but B-fields do not!

    Electric dipole in inhomogeneous electric field
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    Illustration : A dipole (positive + negative charge) is accelerated in the electric field to the positive charge. The dipole gains kinetic energy.
    Lorentz force: electron in a magnetic field
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    Illustration : A moving charge in the magnetic field (pointing into the screen) is forced into a circular path. However, it does not gain energy.