Electric Potential
Đã giới thiệu| English | Ý nghĩa |
|---|---|
| volt/vəʊlt/ | Volt |
Voltage is like "electric height"
- A ball rolls downhill from high ground to low; a positive charge "rolls" from high voltage to low.
- Voltage measures the electric potential energy per unit charge at a point.
- It is like the height of an electric landscape — energy waiting to be released.
- The difference in voltage between two points is what drives current in a circuit.
Potential is energy per charge
- Electric potential $V$ is potential energy per unit charge: $V = \dfrac{U}{q}$.
- Its unit is the volt 伏特 ($1\ \text{V} = 1\ \tfrac{\text{J}}{\text{C}}$).
- Unlike the field, potential is a scalar — just a number at each point, no direction.
- For a point charge, $V = \dfrac{kq}{r}$, falling off as $1/r$.
Field and potential together
See how the field lines relate to the potential that falls off around a charge.
Electric potential is a vector with a direction at each point.
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False. Electric potential is a scalar measured in volts; it is the electric field that has a direction.
One volt equals one joule per ____.
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$1\ \text{V} = 1\ \tfrac{\text{J}}{\text{C}}$ — energy per unit charge.
Equipotentials and potential difference
- Points at the same potential form equipotential surfaces (circles around a point charge).
- No work is needed to move a charge along an equipotential.
- The potential difference $\Delta V$ between two points is the "voltage" between them.
- The energy to move a charge $q$ through $\Delta V$ is $W = q\,\Delta V$.
How much energy is needed to move a $2\ \text{C}$ charge through a potential difference of $6\ \text{V}$? Answer in $\text{J}$.
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$W = q\Delta V = 2 \times 6 = 12\ \text{J}$.
How much work is needed to move a charge along an equipotential surface?
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Points on an equipotential are at the same potential, so no work is needed to move between them.
Select all true statements about electric potential.
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Potential is a scalar in volts, and its difference drives current. Only the field has a direction.
Why it matters for circuits
- A battery maintains a fixed potential difference across its terminals.
- That voltage is the "push" that drives charges around a circuit.
- Charges flow from high potential to low, releasing energy in the components.
- So potential is the bridge from static charges to working circuits (next topic).
Which correctly distinguishes potential from field?
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Potential $V = U/q$ (scalar, volts); field $E = F/q$ (vector, N/C).
Don't confuse potential $V$ (a scalar, in volts) with the field $E$ (a vector, in $\tfrac{\text{N}}{\text{C}}$). Potential is energy per charge; the field is force per charge. And only differences in potential do work — the zero point is your choice.
How much energy does it take to move a $2\ \text{C}$ charge through a potential difference of $6\ \text{V}$?
- $W = q\,\Delta V = 2 \times 6 = 12\ \text{J}$.
That is the energy the charge gains (or gives up), depending on direction.
Electric potential $V = U/q$ (in volts) is the potential energy per unit charge — a scalar, like "electric height". For a point charge $V = kq/r$. The potential difference ($\Delta V$, the voltage) drives current, and moving charge $q$ through it takes energy $W = q\,\Delta V$.
Write from an energy of 24 J
- A 3 C charge moves through a potential difference of 8 V.
- Find the energy transferred.
How much energy is transferred when a 3 C charge moves through a potential difference of 8 V? Answer in joules.
3 times 8 is 24.
How much energy is transferred?
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Charge times potential difference is 24 J. Other options — 12 J (the lesson transfer); 8 J (the voltage used as the energy).