This guide covers essential terms and notations in electricity and electric fields, including quantization of charge, Coulomb's Law, gravitational force, electric flux, dipole moment, and Gauss's Law. These concepts form the foundation of electrostatics in physics.
Basic Notations and Their Units
- e = Elementary charge, 1.602192 × 10–19 C
- me = Mass of electron, 9.11 × 10–31 kg
- q = Charge (SI unit: Coulomb, C)
- 1 C = 6 × 1018 electrons
- 1 μC (micro coulomb) = 10–6 C
- ε0 = Permittivity of free space, 8.854 × 10–12 C2 N–1 m–2
Quantization of Charge
Main Formula: q = ne
Where:
- q = Charge
- n = Number of electrons
- e = Elementary charge on one electron
Coulomb's Law
Main Formula: F = k |q1 q2| / r2
Where:
- F = Force between two charges
- q1 and q2 = Charges
- r = Distance between charges
- k = Constant, 1 / (4π ε0)
Gravitational Force
Main Formula: F = -G |m1 m2| / r2
Where:
- F = Force between two masses
- m1 and m2 = Masses of objects
- r = Distance between charges
- G = Gravitational constant
Electric Field
Main Formula: E = k Q / r2
Where:
- E = Electric field
- Q = Charge producing the field
- r = Distance between charges
Relation Between Force and Electric Field
Main Formula: F(r) = q E(r)
Acceleration of the Electron
Main Formula: ae = eE / me
Where:
- me = Mass of electron
- e = Charge of one electron
- E = Electric field
Electric Flux
Main Formula: Δϕ = E ⋅ ΔS cosθ
Where:
- Δϕ = Electric flux
- E = Electric field
- ΔS = Area element
Field of an Electric Dipole
On Axis: E = k (4 q a) / r3
On Equatorial Plane: E = -k (2 q a) / r3
Dipole Moment
Main Formula: p = q × 2a
Torque on a Dipole
Main Formula: τ = p × E
Surface Charge Density
Main Formula: σ = ΔQ / ΔS
Gauss's Law
Main Formula: Δϕ = E ⋅ ΔS = k q ΔS / r2 = q / ε0
Field Due to a Uniformly Charged Spherical Shell
- Outside the Shell: E = k q / r2
- Inside the Shell: E = 0
Download the Complete Formula List
If you need all these formulas in one document, download the complete list from the link below: