T1 - Electrical Concepts

q

Charge, measured in Coulombs (C)

i

Current, measured in Ampere (A)

v

Voltage, measured in Volts (V)

W

Energy, measured in Joules (J)

p

Power, measured in Watts (W)

R

Resistance, measured in Ohms

C

Capacitance, measured in Farad (F)

L

Inductance, measured in Henry (H)

Current

Rate of flow of charge past a point (coulombs/second, or amperes)

Voltage

Energy change per unit charge moving from point B to A (joules per coulomb, or volts)

Direct Current, DC

Constant current with time

Alternating Current, AC

Current varies over time

Element Absorbs Energy

Flow from positive → negative

Element Supplies Energy

Flow from negative → positive

DC Voltage

Constant voltage with time

AC Voltage

Voltage varies with time

Max Sink Current

Amount of current that can flow into a component without damaging it

Ground Current

V_C = 0V (reference point)

Floating

Non-grounded, can accumulate static charge hence don’t know potential relative to ground

Power

Rate at which energy is absorbed (joules/seconds, or Watts)

Passive Reference Configuration

Current reference direction flows into positive reference polarity (thus p = v x i)

Element Absorbs Power (load)

p > 0

Element Provides Power (source)

p < 0

Conservation of Energy (Power)

Sum of instantaneous power into all elements in a circuit must equal 0.

Node

Point where 2 or more elements join (point of common voltage)

Kirchoff’s Current Law (KCL)

Sum of currents entering any node is 0.

Kirchoff’s Voltage Law (KVL)

Sum of voltages around any loop is 0.

Series

Same current flow through elements, but voltage can be different

Parallel

Same voltage through elements, but current can be different