JC Science - Electricity

What are everyday items made of?

Atoms

Proton

Location: nucleus
Charge: +1

Neutron

Location: nucleus
Charge: 0

Electron

Location: electron shells
Charge: -1

Charged atom

An atom is charged if there is a difference in the number of protons + electrons

Positive charge

more protons than electrons

Negative charge

more electrons than protons

Static electricity

A buildup of charges on an object which then stays static (still). This creates an imbalance of charge on the surface

Electric discharge

The rapid transfer of electric charge from one object to another

When does electric discharge happen

When 2 objects with different amounts of charge are brought close to each other

Current electricity

The flow of electric charge through a circuit

Electric current (measurement + instrument + symbol)

Measurement: Ampere (A)
Instrument: Ammeter
Symbol: I

Potential difference (voltage)

The difference between the electric potential energy at two points in a circuit

Voltage (measurement + instrument + symbol)

Measurement: Volts (V)
Instrument: Voltemeter
Symbol: V

Resistance

The opposition to the flow of electrons in a circuit. Resistance occurs if the flow of electrons is slowed down.

Resistance (measurement + instrument + symbol)

Measurement: Ohms (Ω)
Instrument: Ohmmeter
Symbol: R

Lamp

Lights up

Voltmeter

Measures voltage

Ammeter

Measures the current

Cell

Gives electrons energy. Energy source

Battery

Gives electrons energy. Energy source

Switch

Turns off or on the curreny

Resistor

Slows down the current

Variable resistor

Slows down the current (variable amount)

Motor

Makes something move

Series circuit

-A series circuit only has one path
-The electrons pass through all components
-Electrons share the energy between components

Switches in series circuits

-The switch controls both bulbs
-If one bulb breaks the circuit doesn't work

Parallel circuits

-Parallel circuits have multiple paths/loops
-The electrons splits along different paths
-The bulbs get the full amount of energy (it is NOT shared)

Ohm's Law

-The amount of current passing through a material is proportional to the voltage across the material
-As voltage increases, current increases

Ohm's law equation

R\= V/I
V\= IxR
I\= V/R
Triangle (V: top, R: right, I: left)
Very Important Rule

Fuses

A fuse is a safety device. A fuse is a thin piece of wire that melts if there is a fault in the appliance. If too much current flows through it then the wire melts + stops current flowing.

Voltmeter on a circuit

-A voltmeter is attached to the side
-It measures the difference in current before a resistor and after a resistor

Ammeter in a circuit

-Connected in a series
-It records circuits current

Ohmmeter in a circuit

-Connected in a series

Electrical power

The rate at which electrical energy is produced or consumed

electrical power equation

P\=IxV
I\= P/V
V\=P/I
P: top I: left V: right

What is electrical power measured in

Watts (W)

Power rating

a measurement of how much electrical energy an electrical device consumes for every second it is in use

Bulb

Voltmeter

Ammeter

Battery

Resistor

Variable resistor

Motor

Lamp

Cell

Switch

Ohmmeter

Measures resistance

In electronic circuits there is:

Input, Process, Output
(Input usually received through sensors)

Resistors

-Resistors are used to control the flow of current in a circuit
-Many different types of resistors

What do resistors protect

They protect the more complex electronic components from having too much electric flow in them + damaging them

Light Dependent Resistors (LDR)

-They vary the amount of current that can pass through them depending on the amount of light shining on them
-Little light: high resistance + low current
-Lots of light: low resistance + high current
-Used to detect the amount of fight

LDR uses

Automatic night lights, automatic phone screen brightness

Input + output for LDR

Input: Light level
Output: Amount of current allowed to flow through

Symbol for LDR

Thermistor

A type of resistor where the resistance depends on the temperature

Thermistor uses

Digital thermometers, turning off a boiling kettle, controlling temperature in a house

Thermistor input + output

Input: Temperature
Output: How much current to flow through

Symbol for thermistor

Diode

-Electronic components that only allow current to flow through them in one direction.
-They flow from positive to negative

What are diodes used for

To make sure other electric components aren't damaged by the current flowing in the wrong direction

Forward bias

When diodes are connected in a way that allows current to flow

Reverse bias

When diodes are connected in a way that does not allow current to flow through

Symbol for diodes

Light Emitting Diode LED

Diodes that light up when current is flowing through them

LEDs + current

-LEDs have to be connected in a forward face bias to work
-If too much current flows through then it could break
-LEDs usually have resistors in the circuit for this reason

LED legs

2 legs
Longer leg: connects to positive side of battery
Shorter leg: connects to negative side of battery

Benefits of LEDs

-Use less energy than bulbs
-Last for longer
-Doesn't produce as much heat

Uses of LEDs

-Television screens
-Car indicators + headlights
-Decorative lights

Symbol for LED

Why is it important to know if an electrical appliance is on or not

So you don't waste energy