C03 Electric Field


This applet lets you plant the source charges. The hockey puck is the test charge that is going to be released from rest. It is going to experience electric forces according to the resultant electric field (produced by all the source charges)


The electric field determines the electric force (Fe=qE) and thus the acceleration (a=qE/m) of the puck at every position. But acceleration is not the same as velocity. The banana kick failed because the puck was already moving and had some momentum, and the field was too weak to turn the puck towards the goal.

Many people have the misconception that the field lines shows the path that a charge would take when travelling in the field. Nope. The field lines only shows the direction a charge would take at the instant it is released from rest at that point. It is like if you dropped some thing from rest, it falls vertically downward. But if you toss is side way, it does a parabolic curve. Even though g field is downward.

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