CR, AC and Rectifiers Flashcards
What is an RMS value?
Root Mean Square (RMS) current/voltage is the DC current/voltage that dissipates the same amount of power as the average power dissipated by the AC current/voltage
What does “the current lags on the voltage by 90°” mean?
The current reaches its peak value after the voltage reaches its peak value, and both have reached their peak value at 90°
What does CIVIL represent? What does it help us do?
For a Capacitor, I leads (comes before) V, for and inductor (L), I lags (comes after) V
It helps use remember leading and lagging components
What is the equation that relates inductive reactance, inductance and frequency?
XL = 2 x π x f x L
Inductive reactance = 2 x π x frequency x inductance
What is the equation that relates capacitive reactance, capacitance and frequency?
XC = 1 / (2 x π x f x C)
Conductive reactance = 1 / (2 x π x frequency x capacitance)
What are the four functions of a power supply unit (that converts AC to DC)? What do they do?
Transformer - converts 230V AC (mains) to lower AC
Rectifier - converts AC to fluctuating & unidirectional (always +) voltage (rectified AC)
Smoothing - lessens fluctuations on voltage
Stabilisation - Gives steady flat-line DC
What is a half-wave rectifier?
A simple rectifier that ensures current only flows in one direction (and (graphically) makes only top of sine wave present)
What does the load do in a rectifier?
Registers positive half waves from AC source - current to load is cut off if AC supply is negative
What is one good and bad thing about half wave rectifiers?
Good - easy as only involves one diode
Bad - half AC wave is wasted
What is a full wave bridge rectifier?
A rectifier that uses four diodes arranged in a way to get rectified AC to the load
How does smoothing work?
When voltage from the rectifier rises, current goes to the load and the capacitor is charged. When the voltage falls, the charge in the capacitor supplies current to the load
How does stabilisation work?
Semiconductors (commonly zener stabilised circuits) remove voltage variation after smoothing
What is a CR circuit?
Where one or more capacitors and one or more resistors are combined in a circuit
