Electrons

Orbit nucleus and have a negative charge

Like Charges

Repel

Opposite Charges

Attract

Electric Charge

Given the symbol **Q.** Measured in **Coulombs**(**C**)

Charge of an Electron

-1.6 x10^{-19}C

In an electric field electrons

Accelerate towards a positive voltage and away from a negative voltage

Electric Field Line

Diagram which shows the direction of the force a small positive charge would experience

Field Line Rules

Lines are continuous

Lines never touch or cross

Closer the lines are to each other, the stronger the electric field

Current

Amount of charge flowing through a conductor each second. GIven symbol **I** and measured in **Amperes**(**A**)

Measuring Current

Use an ammeter

Potential Difference (Voltage)

The amount of energy transferred per coulomb of charge. Given symbol **V **and measured in **Volts**(**V**)

Direct Current (d.c.)

Steady voltage provided causing a steady flow of electrons in one direction. Appears as straight line on oscilloscope

Example: Batteries

Alternating Current (a.c.)

Mains or signal generator provides a voltage which changes with a constantly changing direction resulting in electrons moving backwards and forwards

Mains Voltage

Average - 230V

Peak - 325 V

Mains Frequency

50 Hz

Uniform Field

One of Constant Strength

Resistance

Property of a conductor to oppose current. Given symbol **R **and measured in **Ohms**(**Ω**)

Ohm's Law

Current in the resistor is proportional to the voltage across it

Voltage Divider Circuit

2 or more resistors are connected in series, sharing the voltage between them

Non-Ohmic Conductors

Current through the conductor is NOT proportional to the voltage across it. Example - Light Bulb

Light Bulb Resistance

As temperature of light bulb gets bigger its resistance increases

Diode

Semi-conductor that only allows current to flow in one direction. Only conducts when more than 0.7 V is applied

Cell

Transfers chemical energy to electric energy providing electric energy to make charge move in a circuit

Battery

Transfers chemical energy to electric energy providing electric energy to make charge move in a circuit

Resistor

Made from various compounds or resistance wire, designed to limit the current in a circuit

Variable Resistor

Used to vary the current size in a circuit

Fuse

Made with a wire which melts when the current exceeds a limit, designed to break the circuit to protect other components

Lamp

Transfers electric energy into light (and heat)

Motor

Transfers electric energy into kinetic energy

Voltmeter

Measures the voltage across a component

Ohmmeter

Measures the resistance of a component

Series Circuit

All the components are in a single loop

I_{S}=I_{1}=I_{2}=...

V_{S}=V_{1}+V_{2}+...

R_{T}=R_{1}+R_{2}+...

Parallel Circuit

There are junctions and branches. More than one path for current to flow

V_{P}=V_{1}=V_{2}=...

I_{P}=I_{1}+I_{2}+...

1/R_{p}= 1/R_{1 }+ 1/R_{2}+ 1/R_{3}...

Solar Cell

Transfers light energy to electric energy

Microphone

Transfers sound energy into electric energy

Thermocouple

Transfers heat energy to electric energy

Light Dependant Resistor (LDR)

When exposed to light its resistance decreases

Thermistor

When heated its resistance decreases

Relay Switch

When current is passed through it , it closes a metal switch completing a second circuit

Capacitor

Device that stores charge

Bipolar Transistor

When voltage between base and emitter > 0.7V it conducts along the collector as well / turns on

Electrical Switch

MOSFET

When voltage between gate and source >2V conducts along drain-source/turns on

Electrical Switch

Energy

Given symbol **E**. Measured in **Joules**(**J**)

Power

Energy transferred per second. Given symbol **P**. Measured in **Watts** (**W**)

Types of Energy

Heat

Light

Sound

Electric

Gravitational Potential

Nuclear

Elastic

Chemical

Law of Conservation of Energy

Energy can not be created or destroyed but it can be converted ir transferred from one form to another

Potential/Kinetic Conservation Equation

v = √2gh

Electromagnetic Induction

A changing magnetic field around a coil of wire unduces a potential difference

Increasing Induced Potential Difference/Current

Increase magnetic field strangth

Increase speed of movement

Increase number of turns on the coil

Temperature

Measure of the kinetic energy of individual particles in the material. Given symbol **T** and measured in **Degrees Celcius** (**ºC**) or **Kelvin**

Heat Energy

Measure of the combined kinetic energy of all the particles in the material

Specific Heat Capacity

Energy required to change the temperature of 1kg of a material by 1ºC. Given symbol **c** and measured in **Jkg ^{-1}ºC^{-1}**

Specific Latent Heat of Fusion

Energy required to change 1kg of solid at its melting point to 1kg of liquid. Given symbol **l _{f} **and measured in

**Joules per Kilogram**(

**Jkg**)

^{-1}Specific Latent Heat of Vaporisation

Energy required to change 1kg of liquid at is boiling point to 1kg of gas. Given symbol **l _{v}** and measured in

**Joules per Kilogram**(

**Jkg**)

^{-1}Pressure

Force per unit area. Measured in Pascals (**Pa**) and given symbol **P**

Kinetic Theory

Gas made of atoms and molecules

Atoms and molecules move around randomly in all directions

Atoms and molecules collide elastically with each other and walls of container, exerting a small force

As temperature of atoms and molecules increases so does their kinetic energy

Air Pressure

Sum of forces over area of a container or substance. Atmosphere causes 100kPa

Boyle's Law

If the volume of a gas is halved its pressure doubles (assuming constant mass and temperature)

P_{1} x V_{1} = P_{2} x V_{2}

Converting Celcius to Kelvin

Add 273

Absolute Zero

-273ºC or 0K

Pressure Law

If temperature (in kelvin) of gas is doubled its pressure doubles (assuming constant mass and volume)

P_{1}/T_{1} = P_{2}/T_{2}

Charles' Law

If temperature (in kelvin) of a gas is doubled its volume doubles (assuming constant mass and pressure)

V_{1}/T_{1} = V_{2}/T_{2}

General Gas Law

P_{1}V_{1}/T_{1} = P_{2}V_{2}/T_{2}

Kinetic Theory - P+V

As volume increases particles move further apart meaning less frequent collisions with the walls of the container

Total Force Decreases

Area of walls increases

P=F/A so pressure decreases

Kinetic Theory - P+T

As temperature increases particles' kinetic energy increases and they speed up. Means more frequent collisions, each with a greater force

Total Force increases

P=F/A so pressure increases

Kinetic Theory - V+T

As temperature rises the kinetic energy of particles increases. Means more frequent collisions, each with a greater force

Volume must increase to reduce number of collision so pressure is unchanged