Section 6 – Electricity notes
7/1/25
Electricity
Current is flow of charge and is produced by applying a potential
difference.
Electrons carry charge, and conventional current flows the way positive
charges would flow, opposite to electrons.
I is symbol for current, unit is A – amperes.
Q is symbol for charge, unit is C - Coulombs
Current is rate of flow of charge:
I=ΔQ/Δt
1 electron carries 1.6x10-19 C.
Kirchoff’s 1st Law
Current flowing into a junction equals current flowing out of a junction.
(Due to conservation of charge).
Battery does work to move electron to negative side.
Chemical energy is transferred to electrical potential energy.
When the electrons reaches the bulb, it converts electrical potential
energy to thermal and light energy.
Some materials are good conductors as they have an abundance of free
charges, some are good insulators as they have none.
However, an insulator can be turned into a conductor if a large enough
voltage is applied (e.g. lightning through air – an insulator).
Recharging a battery means reversing the chemical process.
Potential difference is work done per unit of charge and is measured in
volts.
“One volt is equivalent to 1 Joule of energy expended or 1 Coulomb of
charge between 2 points”.
V=W/Q
10/1/25
Kirchhoff’s Second Law
,Sum of voltages around a closed loop = 0.
Sources have positive voltages, resistors, lamps, etc. are negative.
14/1/25
Voltage, Power, Current, Energy
Q=It
W=VQ
W=VIt
P=VI (measured in Watts = J/s)
Current measured with an ammeter (A) .
, Ammeters go in series with the current they are measuring.
Ammeters have a very low resistance, so they don’t decrease the
current and don’t take any potential difference.
Volts are measured with a voltmeter (V)
Volt meters go in parallel with the potential difference they are
measuring.
Voltmeters have a very high resistance, so they don’t create a
different path for the current to flow through.
16/1/25
Resistance
Resistance opposes the flow of charge due to collisions between charge
carriers and lattice atoms/ions of the material.
Resistance is directly proportional to voltage and inversely proportional to
current.
Voltage is directly proportional to current.
V=IR
7/1/25
Electricity
Current is flow of charge and is produced by applying a potential
difference.
Electrons carry charge, and conventional current flows the way positive
charges would flow, opposite to electrons.
I is symbol for current, unit is A – amperes.
Q is symbol for charge, unit is C - Coulombs
Current is rate of flow of charge:
I=ΔQ/Δt
1 electron carries 1.6x10-19 C.
Kirchoff’s 1st Law
Current flowing into a junction equals current flowing out of a junction.
(Due to conservation of charge).
Battery does work to move electron to negative side.
Chemical energy is transferred to electrical potential energy.
When the electrons reaches the bulb, it converts electrical potential
energy to thermal and light energy.
Some materials are good conductors as they have an abundance of free
charges, some are good insulators as they have none.
However, an insulator can be turned into a conductor if a large enough
voltage is applied (e.g. lightning through air – an insulator).
Recharging a battery means reversing the chemical process.
Potential difference is work done per unit of charge and is measured in
volts.
“One volt is equivalent to 1 Joule of energy expended or 1 Coulomb of
charge between 2 points”.
V=W/Q
10/1/25
Kirchhoff’s Second Law
,Sum of voltages around a closed loop = 0.
Sources have positive voltages, resistors, lamps, etc. are negative.
14/1/25
Voltage, Power, Current, Energy
Q=It
W=VQ
W=VIt
P=VI (measured in Watts = J/s)
Current measured with an ammeter (A) .
, Ammeters go in series with the current they are measuring.
Ammeters have a very low resistance, so they don’t decrease the
current and don’t take any potential difference.
Volts are measured with a voltmeter (V)
Volt meters go in parallel with the potential difference they are
measuring.
Voltmeters have a very high resistance, so they don’t create a
different path for the current to flow through.
16/1/25
Resistance
Resistance opposes the flow of charge due to collisions between charge
carriers and lattice atoms/ions of the material.
Resistance is directly proportional to voltage and inversely proportional to
current.
Voltage is directly proportional to current.
V=IR
