9702 · 18.5
Electric potential flashcards
Revision flashcards for Cambridge 9702 Electric potential (syllabus 18.5). Flip, recall, then mark a real past-paper question.
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What is absolute electric potential (V)?
The work done per unit positive test charge to move it from infinity to a specific point in an electric field without acceleration.
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Give the formula relating electric potential (V) to work done (W) and charge (Q).
$V = W/Q$
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What is electric potential energy (U)?
The work done to bring a positive charge from infinity to a specific point within an electric field.
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How do you calculate the electric potential (V) at distance $r$ from a point charge $Q$?
$V = \frac{1}{4\pi\epsilon_0} \frac{Q}{r}$
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What is the formula for the electric potential energy (U) between two point charges $Q_1$ and $Q_2$ separated by $r$?
$U = \frac{Q_1Q_2}{4\pi\epsilon_0 r}$
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How does the sign of a source charge affect the potential it creates?
Positive source charges create positive potential; negative source charges create negative potential.
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What are equipotential lines?
Imaginary lines (or surfaces) connecting points in an electric field that all have the same electric potential.
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What is the relationship between electric field lines and equipotential lines?
Electric field lines are always perpendicular to equipotential lines.
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How much work is done when a charge moves along an equipotential line?
No work is done by the electric field, as there is no potential difference.
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How is electric field strength (E) related to potential difference (ΔV) in a uniform field?
$E = \frac{\Delta V}{d}$, where $d$ is the plate separation.
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What is the relationship between electric field strength (E) and the gradient of an electric potential-distance graph?
$E = - \frac{\Delta V}{\Delta r}$ (magnitude $E = |\frac{\Delta V}{\Delta r}|$). The field strength is the negative potential gradient.
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How do you find the total electric potential at a point due to multiple charges?
Calculate the potential due to each charge individually using $V = kQ/r$ and then add them up as scalars, remembering to include their signs. $V_{total} = V_1 + V_2 + V_3 + ...$
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What is an electron-volt (eV)?
A unit of energy equal to the work done on an electron when it moves through a potential difference of one volt. It is the kinetic energy gained by an electron accelerated through 1V. $1 \text{ eV} = 1.60 \times 10^{-19} \text{ J}$.
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What is the electric potential inside a charged hollow conducting sphere?
The electric potential inside a charged hollow conducting sphere is constant everywhere within the sphere and is equal to the potential on its surface.