AP Physics C: Electricity and Magnetism Flashcards: Electric Current
Written by AP Content Team, Verified for 2026 AP Exams, Last updated: May 2026
Review key ideas with interactive flashcards. This set includes 10 cards to help you master important concepts.
How is the general movement of electric charges through a medium described?
The movement of electric charges through a medium is described as an electric current.
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How is the general movement of electric charges through a medium described?
The movement of electric charges through a medium is described as an electric current.
If you know the number of charge carriers per unit volume (n), the charge of each carrier (q), and their average drift velocity ($\vec{v}_{d}$), what physical quantity can you calculate?
You can calculate the current density ($\vec{J}$) using the equation $\vec{J}=nq\vec{v}_{d}$.
What is current density ($\vec{J}$)?
Current density is a vector quantity that describes the electric current per unit area and is related to the motion of charge carriers within a conductor.
Define electromotive force (emf or $\mathcal{E}$).
Electromotive force (emf) is the electric potential difference that drives the movement of charge in a circuit, creating a current.
What is the equation for current density ($\vec{J}$) in terms of charge carrier properties?
The equation is $\vec{J}=nq\vec{v}_{d}$, where n is charge carrier density, q is the charge per carrier, and $\vec{v}_{d}$ is the drift velocity of the carriers.
What is the mathematical formula for electric current (I)?
The equation for current is $I=\frac{dq}{dt}$, representing the rate of flow of charge (q) with respect to time (t).
What causes electric charges to move in a circuit?
Electric charges move in a circuit in response to an electric potential difference, which is also referred to as electromotive force (emf).
What does the derivative in the equation $I=\frac{dq}{dt}$ imply about the nature of current?
The derivative implies that current is the instantaneous rate of change of charge, not necessarily a constant flow over a long period.
Explain the relationship between current and electric potential difference.
An electric potential difference (or emf) provides the 'push' that causes charges to move, and the resulting rate of charge flow is the electric current.
What is electric current?
Electric current is the rate at which electric charge passes through a cross-sectional area of a medium, such as a wire.