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Electric voltage

Definition: The work needed to move a unit positive charge from infinity to the desired point.

Electric Potential of a Point Charge

\[ V = k \frac{Q}{r}\] ➔ \[ V = (8.99×10^9)×\frac { Q }{ r}\]

Properties of Electric Potential:

  • Scalar quantity (has magnitude only)
  • Depends on the distance from the charge
  • Measured in Volt (V)

Practical Example:

A point charge \[ Q = +5\;nC\] Find the electric potential at a distance \[r= 0.3\;m \]

Potential calculation:
\[V = (8.99×10^9) × \frac {5×10^{-9}}{0.3}\]
\[V = 149.83 V \]

Electric Potential Calculation

Point Charge Electric Potential Calculator

Notes:

  • Potential equation: \[V =\frac { k * Q }{ r}\]
  • k: Coulomb's constant \[k=(8.99×10^9)N.m^2/c^2\]
  • Q: Charge value in Coulombs
  • r: Distance from charge in meters
  • Result appears in scientific notation (example: 1.23e+5)
Electric Potential of Point Charges

Electric Potential of Multiple Point Charges

Basic Concept:

The electric potential (V) at a point in space is the amount of work needed to move a unit positive test charge from infinity to that point without acceleration.

For a single point charge:

\[ V =k *\frac { q }{ r}\]

Where:
- k Coulomb's constant
\[k=(8.99×10^9)N.m^2/c^2\] - q: Charge amount (Coulombs)
- r: Distance from charge to the studied point (meters)

For multiple point charges:

\[ V_{total} = Σ V_i = k Σ\frac {q_i}{r_i}\]

Total potential is calculated by algebraic sum of individual potentials for each charge (superposition principle)

Calculation importance:

  • Design of electronic circuits and electrical complexes
  • Analysis of charge systems in capacitors
  • Study of electric fields in biological systems (e.g., ECG devices)
  • Applications in X-ray systems and microelectronics

Practical applications:

  1. Design of electrostatic storage devices
  2. Calculation of capacitor capacitance
  3. Analysis of heart electrical signals
  4. Lightning protection systems
  5. Electron beams in cathode ray tubes

Important notes:

- Potential is a scalar quantity (not vector) → easier to calculate
- Positive charges produce positive potentials
- Negative charges produce negative potentials
- Measurement unit: volt (1 volt = 1 joule/coulomb)

Electric Potential Calculator

Electric Potential Calculator

Charge (µC): Distance (m):



Uniform Electric Potential

Uniform Electric Potential

Scientific Concept:

Uniform electric potential occurs when the electric field is constant in magnitude and direction, resulting in a linear change in electric potential with distance.

Mathematical Relationship:

\[ ΔV = -E × d × cosθ\]
Where:
- ΔV: Potential difference (Volts)
- E: Electric field intensity (Volts/meter)
- d: Distance (meters)
- θ: Angle between field direction and motion direction

Affecting Factors:

  • Electric field intensity (E)
  • Distance traveled (d)
  • Direction of motion relative to the field (θ)

Practical Example:

If there is a uniform electric field with intensity \[E=50 \;v/m\] and a charge is moved 3 meters parallel to the field, the potential difference would be
\[ ΔV = -(50) × 3 × cos(0°) = -150\; V\]

Key Properties:

  • Linear change in potential with distance
  • Direction of steepest potential decrease matches electric field direction
  • Equipotential surfaces are parallel and evenly spaced
  • Electric field is the negative spatial gradient of potential (E = -∇V)

Important Notes:

1. The negative sign reflects the direction of potential decrease
2. Potential increases when moving against the field
3. No potential change occurs when moving perpendicular to the field (θ = 90°)


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