Section 24.2 Electric Potential
Video Lesson 24.2.2. Electric Potential Difference.
Subsubsection Key Ideas
Just like massive objects store gravitational potential energy, charged objects store electric potential energy.
Definition 24.2.3. Electric Potential Energy.
The change in electric potential energy when a test charge \(q_{\text{test}}\) moves through an electric potential difference \(\Delta V\) is written:
\begin{equation*}
\Delta U_E = q_{\mathrm{test}}\Delta V
\end{equation*}
This definition of potential energy intentionally mirrors the definition of electric force \(\vec{F}^E = q_{\mathrm{test}}\vec{E}\text{.}\) The new quantity \(\Delta V\) is known as the electric potential difference and is based on a new scalar field \(V\text{,}\) known as the electric potential, which, like the electric field, is created by the presence of other electric charges.
Definition 24.2.4. Electric Potential Difference.
The electric potential (difference) is a scalar field that influences the energy of a system with charged objects.
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The electric potential is a scalar. It can be positive or negative, and is measured in volts (V).
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The electric potential difference is sometimes called voltage. Any voltage is referring to an electric potential difference.
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The electric potential has a value at every point in space. The value can be different at different points in space.
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The electric potential is measured relative to somewhere. The electric potential, like energy, is only meaningfully expressed as a difference between two points. It is typical to choose a reference location where the potential is zero and then measure the electric potential relative to that point.
Subsubsection Activities
Activity 24.2.1. Sensemaking: Units.
Express the units of the electric potential (volts) in terms of other units with which you are familiar.
Activity 24.2.2. Sensemaking: Numbers.
An alternative unit for energy is the electron-volt (eV): the amount of potential energy change experienced by one electron moving through an electric potential difference of \(1 \mathrm{~V}\text{.}\) Use the definition of the Electric Potential Energy to determine the number of Joules in an electron-volt.
