Force in capacitor

[Chocolatebear89]

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If the the voltage across the capacitor is doubled, the net force on the charge will:

A. decrease by factor of 2
B. remain the same
C. increase by a factor of 2
D. Increase by a factor of 4

So first I though F=qE, and E=V/d. So if voltage is doubled, E should double, and F should double. Is that right?

or

PE=1/2CV^2 = FD, so Force will increase by factor of 4.

or are both wrong?

What if instead of a charge, there is a dipole. What will the net force on the dipole?

 

[bullsfan1986]

I think your first reasoning is right.

 

[Chocolatebear89]

What if instead of a charge, there is a dipole. What will the net force on the dipole?

 

[plzNOCarribbean]

yeah i think your first reasoning is right. Because V=Ed. and E is proportional to V, then since V, doubles then E must double since the distance between the capacitors stays the same. Therefore, if E doubles, then according to F=qE, the force must double.

 

[firecloak]

Your first line of reasoning is right.

The problem with the second line of reasoning, is that force =/= energy
The magnetic force is not the same as the potential energy.

Remember, force is measured in Newtons (kg m/s2), and energy is measured in Joules (kg m2/s2)