I keep getting “Field-potential relationship” questions wrong in Electrostatic Potential & Capacitance. What's the trap?
assuming electric field points toward higher potential.
The usual trap: assuming electric field points toward higher potential. How to avoid it: a positive test charge naturally moves downhill in potential. Go back to the definition — The electric field points in the direction in which potential decreases most rapidly. Along one dimension E_x = -dV/dx; the minus sign carries the direction information.
Key point
Field-potential relationship
Common mistake
assuming electric field points toward higher potential.
Memory tip
a positive test charge naturally moves downhill in potential.
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