Charge Converter

Convert electric charge between coulombs, microcoulombs, ampere-hours, elementary charges, and other electric charge units with scientific precision.

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Electric Charge Units Explained

Coulomb (C)

The SI unit of electric charge. One coulomb is the charge transferred when a current of one ampere flows for one second. Q = I × t.

Common uses: International standards, electrical engineering, physics calculations, electronics.

Ampere-Hour (A·h)

Charge equal to one ampere of current flowing for one hour. 1 A·h = 3600 C. Common in battery capacity ratings.

Common uses: Battery specifications, energy storage, automotive electrical systems.

Microcoulomb (µC)

One millionth of a coulomb. 1 µC = 10⁻⁶ C. Used for small charges in circuits.

Common uses: Capacitor charge, small electronic components, precision measurements.

Elementary Charge (e)

The charge of a single electron or proton. 1 e ≈ 1.602 × 10⁻¹⁹ C. Fundamental constant in physics.

Common uses: Atomic physics, quantum mechanics, particle physics, semiconductors.

Faraday (F)

The charge required to deposit or liberate 1 mole of electrons. 1 F ≈ 96,485 C. Used in electrochemistry.

Common uses: Electrochemical reactions, battery chemistry, electrolysis calculations.

Statcoulomb (stC) / ESU

Electrostatic unit of charge in CGS system. 1 stC ≈ 3.336 × 10⁻¹⁰ C. Used in older physics texts.

Note: Less commonly used with modern SI units.

Charge, Current, and Time Relationship

Electric charge is related to current and time:

  • Definition: Q = I × t (charge = current × time)
  • Current: I = Q / t (coulombs per second)
  • Example: 5 amperes for 2 hours = 5 A × 7200 s = 36,000 C = 10 A·h

Battery Capacity and Charge

Battery capacity is typically specified in ampere-hours:

  • AA battery: ~2000-3000 mA·h = 2-3 A·h
  • Car battery (12V): ~50-100 A·h
  • Phone battery: ~2000-5000 mA·h
  • Laptop battery: ~40-100 W·h ≈ several A·h
  • EV battery: ~40-100+ kW·h ≈ 10,000-30,000+ A·h

Relationship to Power and Energy

Charge relates to electrical energy and power:

  • Energy: W = Q × V (charge × voltage, in joules)
  • Power: P = I × V = (Q/t) × V
  • Battery energy: E = Q × V_nominal

Coulomb's Law - Electrostatic Force

The force between two electric charges:

  • Formula: F = k × (Q₁ × Q₂) / r²
  • k: Coulomb's constant ≈ 8.99 × 10⁹ N·m²/C²
  • Q₁, Q₂: Charges in coulombs
  • r: Distance between charges

Typical Charge Values

  • Charge in 1 second at 1A: 1 C
  • Lightning bolt: 15-350 C
  • Car battery discharge (1 hour): ~60-100 A·h = 216,000-360,000 C
  • Household circuit breaker trip: 15-20 A × 1 second = 15-20 C
  • Static shock: ~0.0001-0.01 C (depends on conditions)
  • Electroplating: Hours of current = thousands of coulombs

Common Applications

Electric charge calculations are essential in:

  • Battery Design: Capacity ratings, discharge curves, lifetime estimation
  • Circuit Analysis: Charge conservation, Kirchhoff's laws
  • Electrochemistry: Plating, electrolysis, cell reactions
  • Power Systems: Energy calculations, billing, load analysis
  • Electronics: Capacitor charging, storage, timing circuits
  • Safety: Electrical safety, shock hazard analysis
  • Plasma Physics: Ion behavior, plasma diagnostics

Conservation of Charge

One of the fundamental laws of physics:

  • Principle: Total electric charge is conserved in isolated systems
  • Kirchhoff's Current Law: Sum of currents into a node equals sum of currents out
  • Charge balance: Σ Q_in = Σ Q_out + Σ Q_stored
  • Implication: Charge cannot be created or destroyed, only transferred