4.2 Work and Energy in Electric Fields

work: energy being transferred from one object to another as a force is applied by the other object over a displacement
when moving charges or charged objects within electric fields:
- work must be done to a charge to move it against an electric field (negative moves against)
- charge gains electric potential energy
- when moving towards the electric field (positive)
- the object producing the field does work on the charge
  - charge’s electric potential energy turns back into kinetic energy
basically, positive moves with the field, so work is done on the field and its potential energy turns back into kinetic energy
- negative moves against the field, so work is done on the charge and it gains potential energy

work required per unit charge to move a positive point charge from an infinite distance to that point
- infinity is used to calculate total work as electric fields have an infinite range
- electric potential only becomes 0 at infinity

AKA voltage
difference in electric potential between one point and another
- work done in moving a charge from the point with lower electric potential to one with higher electric potential
amount of work done (the electric potential) is independent of the path taken, since work is only done parallel to the field
- doesn’t matter what path you take, amount of work doesn’t change

any point connected by a conductor to the Earth has zero potential (grounded, earthed)
- Earth is a neutral object,
- produces no electric field = no work is done as a charge approaches it

energy gained by an electron when it moves through a potential difference of 1 V