# Magnetic Fields

Does a change in magnetic field induce a change in current, or does a change in current induce a change in magnetic field?

And is a change in magnetic flux reliant on current or magnetic field?

Hi @sarah333,

Sorry I didn’t see this before your exam. I hope it went well.

Does a change in magnetic field induce a change in current, or does a change in current induce a change in magnetic field?

Both! A changing magnetic field near a conductor (normally a piece of metal) will induce a voltage (a force acting on the charges in the metal). If the conductor is a loop, this voltage can drive a current. Note, the magnetic field can be changing to cause this, or the metal can be moving through a changing flux, or a combination of the two. I would normally say “charges experiencing a changing magnetic field will experience a Force, inducing a vltage that may drive a current.”

As moving charges generate their own magnetic field, a changing current would cause a change in the magnetic field it. Decreasing the current would decrease the strength of the magnetic field and vice versa.

And is a change in magnetic flux reliant on current or magnetic field?

Magnetic flux can be thought of as the concentration of magnetic field lines that pass through a given area. So increasing the current through a wire would increase the magnetic flux around the wire. A standard magnet would have it’s own magnetic field, so an area a fixed distance away from the magnet would have a set measurement of flux. An area closer to the magnet would have a higher concentration of magnetic field lines, so a higher flux. If the area you were considering was stationary, but you moved the magnet away, the magnetic field lines through that area would spread out, decreasing the total number of magnetic field lines through the area, so the flux would drop. I realise that may be tricky to follow, so you might find this video helpful.