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π Electric Potential due to a Point Charge
The electric potential, often denoted as $V$, at a distance $r$ from a point charge $q$ is given by the formula:
$\qquad V = \frac{kq}{r}$
where $k$ is Coulomb's constant ($k \approx 8.99 \times 10^9 \text{ N m}^2/\text{C}^2$). From this equation, we can see that the electric potential $V$ is inversely proportional to the distance $r$ from the point charge.
π Graphing Potential vs. Distance
When graphing electric potential ($V$) against distance ($r$) from a point charge, we observe a hyperbolic relationship. Hereβs what you need to know:
- π Shape of the Graph: The graph is a hyperbola. As $r$ increases, $V$ decreases, approaching zero as $r$ approaches infinity.
- π Important Points: Close to the charge (small $r$), the potential $V$ is very large. As you move away (large $r$), the potential $V$ becomes smaller.
- β/β Sign of the Charge: For a positive charge, the potential is positive; for a negative charge, the potential is negative. This affects which part of the hyperbola you see on the graph.
β‘ Electric Potential vs. Electric Field
It's important to distinguish between electric potential ($V$) and electric field ($E$). Hereβs a comparison:
| Feature | Electric Potential ($V$) | Electric Field ($E$) |
|---|---|---|
| Definition | The electric potential energy per unit charge at a point in space. | The force per unit charge experienced by a test charge at a point in space. |
| Nature | Scalar quantity (magnitude only) | Vector quantity (magnitude and direction) |
| Formula (Point Charge) | $V = \frac{kq}{r}$ | $E = \frac{kq}{r^2}$ |
| Dependence on Distance | Inversely proportional to distance ($V \propto \frac{1}{r}$) | Inversely proportional to the square of the distance ($E \propto \frac{1}{r^2}$) |
| Graph (vs. Distance) | Hyperbolic decay | Quadratic decay |
π Key Takeaways
- π Inverse Relationship: Electric potential decreases as you move away from the charge.
- π Graph Shape: The $V$ vs. $r$ graph is a hyperbola, reflecting the inverse relationship.
- β/β Sign Matters: The sign of the charge determines the sign of the potential.
- π‘ Scalar vs. Vector: Remember that potential is a scalar, while the electric field is a vector.
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