Charge and Fields_1

Charge and Fields_1

1. Electric Fields

   • Acts radially (unless simplified model is being used)
   • Field strength equates to the potential gradient.
   • Field lines always go from positive potential to negative potential, as this is the direction in which a positively charged particle would feel a positive force (shown by arrow head)
   • Only affects charged particles

2. Gravitational Field

   • Force arising from 2 (or more) masses.
   • Forces act towards the centre of mass
   • Universal law of gravitation -GM1m2/r squared
   • Always acts radially (unless using the simplified model of the Earth)
   • Only affects massive particles (which is pretty much everything)

3. Magnetic Field

   • a magnetic field will induce a current in any conducting material.
   • Only affects charged particles
   • induced emf = -N x change in flux/change in time
   • when a mag. field induces a current, the current then induces a magnetic field to oppose the original. Lenz's law!
   • The force carrier for the electromagnetic force is the photon
   • Flux lines always emerge from a north pole and enter the south pole. They can never cross.
   • On a coil, the north face is the face in which the current is moving anticlockwise, and the south pole is the face at which it is moving clockwise

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