Section 21.5 Electric Field
Subsubsection Key Ideas
Definition 21.5.2. Electric field.
The electric field is a vector field that influences the force that a charged object experiences.
-
The electric field is a vector. Like other vectors, it has a magnitude and a direction.
-
The electric field has a value at every point in space. Either the magnitude or the direction (or both) can be different at different points in space.
-
The electric field influences electric charge. The motion of charged objects through space is governed by an electric force acting on the charged object by any pre-existing electric fields.
Definition 21.5.3. Electric force.
The electric force on a point-like object (often called a test charge) is the product of the object’s charge and the electric field at the location of the object:
\begin{equation*}
\vec{F}^E = q_{\text{test}} \vec{E}
\end{equation*}
Analogy with Gravity.
Like the gravitational force, the electric force is a non-contact force, as opposed to a contact force. The electric and gravitational fields are responsible for the force between charges and masses, respectively. In fact, the mathematical structure of the forces are directly analogous:
\begin{equation*}
\vec{F}^E = q_{\text{test}} \vec{E}
\end{equation*}
\begin{equation*}
\vec{F}^g = m_{\text{test}} \vec{g}
\end{equation*}
Subsubsection Activities
Activity 21.5.1. Fields in Science.
An electric field is a field, which means it has a potentially different value everywhere in space. Identify one other quantity you are familiar with that could be described as a field. It can be from physics or from another science, or from your everyday experience. Explain why you believe the quantity you chose is a field.
Activity 21.5.2. Sensemaking: Units.
What are the units of the electric field?
Activity 21.5.3. How Flowers Talk to Bees.
Watch
this video describing how flowers and bees communicate. Can you think of other ways in which plants and animals might rely on, use or be affected by electric fields?
References References
[1]
"How flowers talk to bees 😯" YouTube, uploaded by ByteBrilliance, 17 January 2024, https://www.youtube.com/watch?v=ee381dCP6JM&ab_channel=ByteBrilliance
