Electrical and Electronic Systems

All topics combined into one set - I recommend doing each topic separately first

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 (for power)

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

Voltage Source (DC and battery)

Resistor

Capacitor

Inductor

Impedence

Diode

LED

Zener Diode

Transistor

Operational Amplifier

Resistor Properties

Limit current, convert potential energy to heat/noise, induce a voltage drop

Ideal Resistor

Characteristic plot of I against V is straight line w/ slope of 1/R

Conductance

Reciprocal of resistance (siemens, S)

Open Circuit

Zero conductance, infinite resistance (hence, v=0)

Short Circuit

Zero resistance, infinite conductance (hence, v=0)

Power Rating

Maximum power (in Watts) that a resistor can take before becoming damaged

Voltage Source

Produces a voltage across its terminals, may be constant or a function of time

Properties of Voltage Source

Will deliver any amount of current needed to maintain voltage

Current Source

Produces a specified current regardless of voltage across it, may be constant value or function of time

Zero Volt Voltage Source

Equivalent to short circuit (0 voltage regardless of current)

Zero Amp Current Source

Equivalent to open circuit (0 current regardless of voltage)

Incompatible Model

Ideal current source connected in series w/ source of different value

Incompatible Model

Ideal current source connected in series w/ open circuit

Incompatible Model

Ideal voltage source connected in parallel w/ source of different value

Incompatible Model

Ideal voltage source connected in parallel w/ short circuit

Compatible Model

Voltage sources in series can be combined

Compatible Model

Current sources in parallel can be combined

Real Voltage Source

As load draws more current, voltage across resistor increases, hence voltage available for load decreases

Controlled (Dependent) Sources

Output depends on a voltage or current elsewhere in the circuit

VCVS (Voltage Controlled Voltage Source)

CCCS (Current Controlled Current Source)

VCCS (Voltage Controlled Current Source)

CCVS (Current Controlled Voltage Source)

Resistors in Series

R_eq = R₁ + R₂ + …

Resistors in Parallel

R_eq = 1/(R₁^-1 + R₂^-2)

Voltage Divider

Find voltage across one of two resistors in series.

Current Divider

Find current across one of two resistors in parallel.

Ampere-hours (Ah)

Unit for measuring storage capacity

Stored Energy

Stored charge x voltage

Internal Resistance

Model the decrease in voltage due to increasing current as this (in battery)

Lower Internal Resistance

Supplies a load current with lower voltage drop

Measure open circuit voltage

How to find the value of supply voltage (V_s) of battery

Measure Terminal Voltage

How to find the value of internal resistance (R_s) of battery

Power Transfer

Efficiently transferring energy from a source to a load

Efficiency

P_out/P_in

Energy Loss

Proportional to I²R

Reduce I and R

Reducing energy loss in a circuit

Efficiency = 50%

Maximised P_out

Capacitor

Device that stores charge and energy, comprised of 2 closely spaces parallel plates

Equal and opposite charges flow onto places

Effect of applying a potential difference over capacitor

Farads, F

Units for Capacitance, C

Capacitor at DC

Behaves like an open circuit

Ideal Capacitor

Charge remains indefinitely

Instantanenous change in voltage impossible

Condition for capacitor

RC Circuit

Contains a resistor and capacitor only

RC Circuit Properties

Capacitor will discharge, v_c decreases, and resistor absorbs energy

Tau = RC

Time constant in an RC circuit

63%

Capacitor voltage decay after tau seconds in RC circuit

Capacitors in Parallel

C_eq = C₁ + C₂ + C₃

Capacitors in Series

C_eq = 1/(C₁^-1 + C₂^-1 + C₃^-1)

Inductor

Device that produces a magnetic field around the wire when current passes through

Magnetic Flux Density

Proportional to current and number of turns (N)

Flux Density Changes

Potential difference is induced at terminals

Henries, H

Unit for Inductance, L

Inductor at DC

Behaves like a short circuit

Constant Current through Inductor

No induced potential difference, v(t)=0

Instantaneous change in current impossible

Condition for inductor

Energy Stored in Magnetic Field

Dependent on current and inductance, E(t) = ½Li²(t)

Current Increases

Energy in inductor is being stored

Current Decreases

Energy in inductor is being released

RL Circuit

Contains an inductor and resistor only