Wright State University Lake Campus/2017-9/Phy2410/Brief equations T4

From Wikiversity
Jump to navigation Jump to search

00-Mathematics for this course[edit]

   Measured in radians, defines angle (in radians). The circumference of a circle is and the circle's area is is its area. The surface area of a sphere is and sphere's volume is


  • Earth's gravitational acceleration = g ≈ 9.8m/s2. Speed of light = c ≈ 3×108m/s. The electron has charge, e ≈ 1.6 × 10−19C and mass ≈ 9.11 × 10-31kg. 1eV = 1.602 × 10-19J is a unit of energy, defined as the work associated with moving one electron through a potential difference of one volt.
  • ≈ 8.987× 109 N·m²·C−2 is a fundamental constant of electricity; also ≈ 8.854 × 10−12 F·m−1 is the vacuum permittivity or the electric constant.
  • = 4π × 10−7 NA ≈ 1.257 × 10−6 N A (magnetic permeability) is the fundamental constant of magnetism: .

18-Electric charge and field[edit]

  • is Coulomb's law for the force between two charged particles separated by a distance r: ke≈8.987×109N·m²·C−2, and ε0≈8.854×10−12 F·m−1.
  • is the electric force on a "test charge", q.

Consider a collection of particles of charge , located at points (called source points), the electric field at (called the field point) is:

  • is the electric field at the field point, , due to point charges at the source points, , and points from source points to the field point.

is the electric field due to distributed charge, where , and denote linear, surface, and volume density (or charge density), respectively. Line element:.

19-Electric Potential and Electric Field[edit]

  • is the potential energy of a particle of charge, q, in the presence of an electric potential V.
  • (measured in Volts) is the variation in electric potential as one moves through an electric field . If the field is not univorm, then
  • is the (equal and opposite) charge on the two terminals of a capacitor of capicitance, C, that has a voltage drop, V, across the two terminals.
  • is the capacitance of a parallel plate capacitor with surface area, A, and plate separation, d. This formula is valid only in the limit that d2/A vanishes. If a dielectric is between the plates, then ε>ε0≈ 8.85 × 10−12 due to shielding of the applied electric field by dielectric polarization effects.
  • is the energy stored in a capacitor.
  • is Gauss's law for the surface integral of the electric field over any closed surface, and is the total charge inside that surface.

20-Electric Current, Resistance, and Ohm's Law[edit]

  • defines the electric current. is Ohm's Law relating I, and resistance, R, to the difference in voltage, V, between the terminals. is the power dissipated as current flows through a resistor. Power is the rate at which energy is transformed.