Electric potential

Electric potential energy

Chrisbania Vargas

The electric potential V is the amount of work/energy needed per unit of electric charge to move the charge from a reference point to a specific point.

Electric potential

For example, if we wanted to move a positive charge from point A to point B in the electric field shown in the figure, we would have to do work on the charge, since the electric field would push against us.

ΔV = W / q
Measured in joules/coulomb or volts

Electric potential

If we place the charge q at point B and let it go, it will 'fall' toward point A.
We say that positive charges naturaly want to move from a point of high potential (B) to one of low potential (A).
We can write the electric potential due to a source charge Q at a distance r from the source charge:

V = k Q / r

Electric potential

There exists an electrical potential energy between two charges q₁ and q₂ which is equal to the work needed to bring the two charges from an infinite distance apart to a separation distance r:
U_E = k.q_1.q₂ / r
U_E = W = q.V
q is the charge being moved in the electric field of the other charge.

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​Electric potential energy

​Is a region of space where the strength and direction of an electric field are the same at every point.
E = V / d
Unit = volts/meter

Uniform electric field

Multiple Choice

Consider the electric field diagram. Estimate what the magnitude of the charge on the right is in all cases. The charge on the left is +3μC.

• -3μC
• +3μC
• 0μC
• +1μC

Multiple Choice

Consider the electric field diagram. Estimate what the magnitude of the charge on the right is in all cases. The charge on the left is +3μC.

• -3μC
• +6μC
• +3μC
• 0μC

Multiple Choice

Consider the electric field diagram. Estimate what the magnitude of the charge on the right is in all cases. The charge on the left is +3μC.

• +3μC
• +1μC
• -1μC
• -3μC