Why isn't the work always 0 in a uniform electric field

[September24]

In a uniform electric field, as we move a charge around say... Between two plates, doesn't it feel the same electric field at every position?

Therefore it feels the same force everywhere? If that it the case, how come voltage isn't the same everywhere. For example , if the plates are 10 cm apart, if we move the charge from position 3 to position 5, why isn't the work 0. If the E field is uniform, then voltage should be too right?

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[FindMeOnTheLinks]

Work=Fd. Since the electric field is constant at every point between the plates, the force is constant as well. The force acts on the charge even if the force doesn't change. If the charge moves, work is done per the equation W=Fd

As for voltage, an electric field necessarily points from a location of high electric potential to a location of lower electric potential. Thus the voltage must change.

 

[NextStepTutor_2]

High September24,

Remember that electric field has a direction associated with it. It points in the direction in which a positive charge would move if placed in that electric field.

Force= Electric Field x q

where q is the amount of charge, in coulombs. Electric field can be expressed as newtons/coulomb ("newtons per coulomb").

As you mention, the charge does feel the same force everywhere in a uniform electric field. Voltage, however, is the potential ENERGY per coulomb. So

Voltage = Electric field x distance

where electric field is, again, measured in newtons/coulomb and distance is in meters. When you multiply those units together, you have
(newtons x meters)/ (coulomb)
Since newtons x meters is joule (the unit for energy), this is energy per charge.

Since the charge experiences a force everywhere in the electric field and will move a distance because of the electric field, it does, indeed, experience a potential energy change (recall: force x distance moved = energy). Because voltage is defined as potential energy for a unit of charge, there must be a change in voltage.



Also, for some resources that go through concepts like this, feel free to check out this link
<http://forums.studentdoctor.net/threads/mcat-study-strategies-and-study-plans.1053555/>

I hope this helps!