Basics of electronics

why electronics

virtually all measurements use electronics to aquire data/ store data/ process data

sensors vary their output based on measurand value

water flow analogy

charge → water volume

voltage → water pressure

current → water flow

resistance → water pipe resistance

electical current

aka flow rate of electrical charge (unit = ampere A)

i = dq/dt

electrical charge (q) is physical property that causes a particle to move due to electromagnetic forces (unit = coulomb C)

Coulomb’s law

defines the force acting between elec charged particles separated by distance r

Charge q is locally conserved, so within an electrical circuit there will always be the same amount

even though charge is conserved, current aka speed can vary

Electrical voltage

to move water in pipe you need pressure → to move charge in circuit you need work → comes from electrical potential (nrj)

V is the difference in elec potential energy, per unit charge between two points

also known as elec pressure

Electrical resistance

measure of how much electrical potential can be moved for a given flow rate

typically related to number of free electrons

→ high resistance means slower flow rate of charge for given potential

Ohm’s law

Pouillet’s law

water is easier to push than maples syrup (less dense)

resistance of a material R can be related to the resistivity via Pouillet’s law

resistors

= physical devices ued to create resistance in circuit

usually have a tolerance to stated resistance +- 5%

Electrical power

= rate at which we do work required to move the electrons

can relate electrical power to heat (Joule heating)

knowing power = important bc if too much component it can burn out

electrical capacitance

= the ability of component/circuit to collect and store energy in the form of elec charge (unit= farads F)

the rate at which charge is released/stored depends on capacitance and voltage applied

→ capacitors therefore resist sudden voltage changes

small capacitance implies fast discharge rate

Electrical inductance

= the rate of change of magnetic flux due to a change in current (unit= Henry H)

inductors is the physical device that creates this → inductors resist changes to current

L = d(magnetic flux)/di

concept of inductance

as electrons flow through wire, they also create electromagnetic field around it

→ this may interfere with the electric signal we’re using for our measurements → why we need to care

but can be advantage ex: magnetic proximity sensor

concept of impedance

three key devices used in circuits:

resistorrs → provide resistance to circuits

capacitor → sotre charge when a voltage is applied

inductors → produce a magnetic flux when a current passes

all these produce effective resistance on elec circuit called impedence