ElectricityAndrew Wallace

Overview Electricity Units AC/DC

Height - potential Flow - current Width - resistance

Electricity Voltage (EMF) – height

V in Volts Current – flow

I in (milli) amps Resistance – width

R in Ohms (W) Controlling the Flow

Controlling the Flow U = IR U = voltage I = current R = Resistance Ohms Law

Example : I = 10 mA and R = 1 kW U = 10 mA * 1 kW = 10 V

Controlling the Flow Resistors

Wire Carbon Power rating Value – colour rings

Units What sizes do we use to measure

things? Nano - n Micro - m Milli - m Killo - k Mega - M

UnitsT G M k …, m m n p

12 9 6 3 -3 -6 -9 -12

Voltage Direct Current (DC) Alternating Current (AC)

Voltage Direct current

Flow Batteries

cells DC generators

Voltage Alternating

current Flow AC Generators Circles, triangles

and waves!

Voltage

Voltage

amplitude

Wave length

Voltage How many wave lengths do we have

each second? Herts (Hz)

F = 1/t

F = 300 / wave length (l) in MHz

Power How much work can we do?

Power (P) Current Voltage Watts (W)

P = IU

Power I = 2 mA U = 5 V P = IU = 2 mA * 5 V = 0.01 W

P = 5 W U = 24 V I = P / U = 5 W / 24 V = 0.208 A

Questions?