Search results
Results from the WOW.Com Content Network
A Magic Triangle image mnemonic - when the terms of Ohm's law are arranged in this configuration, covering the unknown gives the formula in terms of the remaining parameters. It can be adapted to similar equations e.g. F = ma, v = fλ, E = mcΔT, V = π r 2 h and τ = rF sinθ.
Its current-voltage relation is obtained by exchanging current and voltage in the capacitor equations and replacing C with the inductance L. DC circuits [ edit ]
The capacitance of a capacitor is one farad when one coulomb of charge changes the potential between the plates by one volt. [1] [2] Equally, one farad can be described as the capacitance which stores a one-coulomb charge across a potential difference of one volt. [3] The relationship between capacitance, charge, and potential difference is linear.
In electromagnetism, displacement current density is the quantity ∂D/∂t appearing in Maxwell's equations that is defined in terms of the rate of change of D, the electric displacement field. Displacement current density has the same units as electric current density, and it is a source of the magnetic field just as actual
The equation is a good approximation if d is small compared to the other dimensions of the plates so that the electric field in the capacitor area is uniform, and the so-called fringing field around the periphery provides only a small contribution to the capacitance.
It is the time required to charge the capacitor, through the resistor, from an initial charge voltage of zero to approximately 63.2% of the value of an applied DC voltage, or to discharge the capacitor through the same resistor to approximately 36.8% of its initial charge voltage.
The definition of capacitance (C) is the charge (Q) stored per unit voltage (V).= Elastance (S) is the reciprocal of capacitance, thus, [1]= . Expressing the values of capacitors as elastance is not commonly done by practical electrical engineers, but can be convenient for capacitors in series since their total elastance is simply the sum of their individual elastances.
The capacitor will be discharged to about 36.8% after τ, and essentially fully discharged (0.7%) after about 5τ. Note that the current, I, in the circuit behaves as the voltage across the resistor does, via Ohm's Law. These results may also be derived by solving the differential equations describing the circuit: