Understanding Electricity: Concepts and Safety

STATIC ELECTRICITY

the BUILD UP of electrons on a surface

CURRENT ELECTRICITY

the FLOW of electrons along a conductor e.g. copper wire

ELECTRICAL CIRCUIT

a path along which electrons travel and deliver their energy

ENERGY SOURCE

examples include batteries and power points

Current

the RATE at which electrons are flowing in a circuit

Voltage

the DIFFERENCE in charge between two points

Resistance

a force that OPPOSES current

High resistance

results in LOW current

Series circuits

have ONE path for current

Voltage in series circuits

is SHARED between components

Resistance in series circuits

ADDS UP to give total resistance

Parallel circuits

have MULTIPLE paths for current

Current in parallel circuits

is PROPORTIONAL to its resistance

Voltage in parallel circuits

is the FULL voltage of the battery

Resistance in parallel circuits

does NOT add up to the total resistance

Combination circuits

are made of components in both series and parallel

Household wiring

is one large parallel or combination circuit

Active wire

brings current in, typically brown

Neutral wire

takes current out, typically blue

Earth wire

is a safety device that prevents electrocution, typically green and yellow

Fuses

are single-use devices that break the circuit when excessive current flows

Circuit breakers

protect electrical systems by cutting off power when detecting overloads

Safety switches

protect individuals from electric shock by interrupting power supply when a leak is detected

Parallel circuits

Allow individual branches to receive independent voltage and be controlled separately.

Household wiring colors

Brown = Active, blue = Neutral, green and yellow = Earth.

Fuses

Devices in modern appliances with wires that melt at high temperatures, breaking the circuit to reduce the likelihood of house fires and electrocution.

Safety switches

Work to prevent electrocution in people.

Circuit breakers

Work to prevent appliances from overheating, which reduces the risk of fire.

Electromagnetism

An electric current produces a magnetic field; when current moves along a wire, it generates a circular magnetic force around it.

Solenoid

A coil of wire with electricity flowing through it.

Electromagnets

Created by placing an iron rod or a magnetic material in the center of a coil, strengthening the magnetic field.

Electric motors

Convert electrical energy to kinetic energy by placing a solenoid on a swivel between a permanent magnet.

Generators

Use kinetic energy to produce electrical energy by manually spinning either the magnet or solenoid.

Turbines

Need to be spun at high speeds; larger generators spin their magnets while keeping their solenoids fixed.

Hydro-electricity

Water flowing down spins the turbine.

Steam power plants

Act like large gas kettles where water is heated and turned into high-pressure steam that turns the turbine.

Dynamos

Small magnets spun around a solenoid, often used to power lights of bicycles.

AC/DC

Batteries and solar cells produce direct current (DC), while generators, dynamos, and turbines produce alternating current (AC).

Electricity in AC

Changes direction 50 times every second.

Power plants

Produce electricity at 20,000V.

Electricity Transmission

Electricity must be transmitted from the power plants to homes/businesses.

Resistance in Wires

Wires that transport electricity have resistance, resulting in 'wasted' energy, especially over long distances.

Electric Current

An electric current produces a magnetic field.

Solenoid

A coil of wire with electricity flowing in it is called a solenoid.

Electric Motors

Electric motors convert electrical energy into kinetic energy.

Generators

Generators convert kinetic energy into electrical energy.

Ohm's Law

Ohm's law can be used to find the current, voltage or resistance in a circuit if the other two variables are known.

Series Circuits - Current

In a series circuit, the current flowing through the whole circuit is the same.

Series Circuits - Voltage

In a series circuit, the voltage supplied by the battery is shared by all components.

Series Circuits - Resistance

In a series circuit, the resistance of each component adds up to give the total resistance.

Parallel Circuits - Voltage

In parallel circuits, each branch gets the full voltage of the battery.

Parallel Circuits - Current

In parallel circuits, each branch draws a current proportional to its resistance.

Parallel Circuits - Resistance

In parallel circuits, you do NOT add the resistance of different branches together.

Combination Circuits

Combination circuits are made of components in both series and parallel.

Voltage in Combination Circuits

The circuit is powered by a 9V battery.

Resistance of Bulbs

Assuming each bulb has a resistance of 2Ω.

Total Current Calculation

Calculate the current in each branch and deduce the total current flowing through the circuit.

Voltage Received by Bulbs

Find the voltage received by each globe in this circuit.

Current Flowing Through Bulbs

Find the current flowing through each branch.

Household wiring

A household is one large parallel or combination circuit.

Active wire

Brings electricity in, colored brown.

Neutral wire

Takes current out, colored blue.

Earth wire

Prevents electrocution, colored green and yellow.

Fuses

Devices with wires that melt at high temperatures, breaking the circuit.

Safety switches

Designed to protect you from electrocution by detecting leaking current in 0.03 seconds.

Circuit breakers

Designed to protect the wiring and circuitry of your house by cutting the power when too much current is present.

Direct Current (DC)

Electrons flow in the same direction, e.g., battery.

Alternating Current (AC)

Electrons shuffle back and forth, e.g., power points.

Ammeter

Measures the amount of charge (electrons) flowing through it per second.

Voltmeter

Measures voltage, the difference in charge between two points.

Energy source

Supply voltage from which electrons gain their energy.

Transformer

Used to reduce voltage for an appliance.

Multiple cells/Batteries

Connecting multiple batteries next to each other makes their voltage add up.

Wet cells

Conducting electrodes submerged in liquid electrolyte.

Dry cells

One electrode wrapped in another, small and don't leak.

Photovoltaic cells

Convert solar energy into electrical energy.

Resistance

A force that opposes current, measured in ohms (Ω).

Ohmmeter

Measures resistance.

Resistance: wires

Connecting wires also have resistance.

Resistance

A force that reduces current in a circuit.

Current

The rate at which electrons flow in a circuit.

Resistors

Circuit components used to reduce the current flowing in a circuit.

Variable resistors

Resistors that allow you to change their resistance to control current.

Conductors

Materials that allow electrons to flow easily, such as metals.

Insulators

Materials with high enough resistance to block the flow of electrons.

Electric charge

The property of electrons that allows them to move and create electricity.

Static Electricity

The build-up of electrons that have been displaced on a surface.

Current Electricity

The flow of electrons along a conductor, such as copper wire.

Simple Electric circuits

A path along which electrons travel and deliver their energy.

Closed circuit

A complete circuit that allows electrons to flow.

Open circuit

A circuit with a break that prevents electrons from flowing.

Energy source

Components like batteries or power points that provide energy in a circuit.

Energy user

Devices like light bulbs or motors that use energy in a circuit.

Electrons

Small, negatively-charged particles that are part of atoms.

Atoms

The basic units of matter, made up of protons, neutrons, and electrons.

Protons

Sub-atomic particles with a positive charge located in the center of the atom.

Neutrons

Sub-atomic particles with no charge located in the center of the atom.

Copper

A good conductor of electricity, commonly used in circuits.