circuits Flashcards
whats a time constant?
the time to increase the charge stored
by 63% of the difference between initial charge and full charge
when can an uncharged capacitor be considered to be fully charged
after a time approximately equal to
5T
whats a capacitive reactance
the opposition of a capacitor to changing current
whats lenz law
that the induced current is always in such a direction as to oppose the charge that is causing it.
whats the implications of lenz law
the magentic field around a current-charging coil will cause a force that will oppose the motion of the magent towards the coil.
whats back emf
self-induced EMF which always opposes the charge in current in the inductor
whats inductance
the oppose of the flow of ac
what is self inductance of a coil
when the current changes, the magentic field changes and an EMF is induced in the coil.
where is energy stored in the magnetic field
around a current-carrying inductor
when does a dc circuit charge
when switch s is closed
why does it take longer for a DC circuit to charge with an inductor
as the current through the inductor is charging and so back EMF is induced, which opposes the increase in current.
why does it take longer for a DC circuit to discharge with an inducto
when the switch is switched off and the power supply is connected, the current decreases. the change in current produces a back EMF that opposes the chnage, resulting in it taking longer.
whats inductive reactance
the opposition of an inductor to changing current
As the ac supply frequency increases…
the self inductance back EMF increases, the inductive reactance increases and current decreases.
As the ac supply frequency decreases…
the self inductance back EMF decreases, the inductive reactance decreases and current increases.
