Friday, 27 February 2015

6c) Electromagnetism

Magnetic fields in current-carrying wire:
  • an electric current in a material produces a magnetic field around it 
  • the larger the electric current, the stronger the magnetic field 
  • the direction of the magnetic field depends on the direction of the current 
Paper Two-
Straight wire, Flat circular coil and Solenoid:

The magnetic field around a straight wire is circular:
Image result for straight wire magnetic field
The magnetic field around a flat circular coil ellipses (egg-shaped):
Image result for flat circular coil magnetic field
The magnetic field around a solenoid  is electromagnet: 
Image result for solenoid magnetic field

If something with a charge is moving across a magnetic field it will 
experience a force from the field, unless it's parallel. 

D.C. Electric Motor (simple):
  • wire in magnetic field 
  • force turns a 'split ring communicator' ---> charge goes from brushes in wires 
      Four factors
  1. more current 
  2. more turns on coil 
  3. stronger magnetic field 
  4. soft iron core 
Loudspeaker:
  • force pushes current away from field, pushes core which makes sound ---> cone vibrates 
The left hand rule:
Helps to figure out the thrust/motion, field and current of the wire to then work out which way the force is acting.
Image result for left hand rule

Wire in magnetic field increase (<) current = more force on wire 
Wire in magnetic field increase (<) strength = more force on wire 


6b) Magnetism

 Paper Two- 
Repel and attract

Opposite poles attract to one another:
Image result for opposite poles attract

Same poles repel one another:
Image result for opposite poles attract

Magnetic substances can also be attracted by a magnet

Properties of a magnetic material

Magnetically hard material ---> retains its magnet properties for a long period of time/permanent. hard to demagnetise

Magnetically soft material ---> loses its magnetic properties almost as soon as the magnet field leaves

Magnetic field lines:

  • represent shape and direction of magnetic field 
  • gives an idea of magnetic field 
Induced Magnetism;
When a magnet is brought near a magnetic material then the material will acts as a magnet because the magnetic field encourages them to align and form poles. Examples: iron, cobalt and nickel. 

The closer the magnet, the stronger the induced magnetism becomes. 

Experiments to find the magnetic field pattern of a permanent magnet and two bar magnets:
Can use multiple compasses or iron fillings to see the magnetic field.

Image result for iron filings on bar magnet     Image result for iron filings on a magnet

Hold two opposite poles close together so that they attract
and makes a uniform magnetic field:
Image result for uniform magnetic field

Wednesday, 25 February 2015

6a) units


  • Ampere (A) 
  • volt (v) 
  • watt (W) 

Section 6

Magnetism and electromagnetism

5d) Ideal gas molecules

Particle theory says that gases consist of very small particles which are constantly moving in completely random directions.

Brownian motion supports the particle theory because large, heavy particles can be moved with Brownian motion with smaller, lighter particles travelling at a high speed. This is way particles appear to be moving around randomly when you observe them in a lab.

Gases have a random motion, so when they collide with something they exert a force on it, and their momentum and direction change.
In a sealed container gas particles smash particles against the container walls- this creates an outward pressure. The pressure depends on how fast the particles are going and how often they hit the walls (average speed)

Absolute Zero
The coldest that anything can get is -273℃ - this temperature is called/ known as the absolute zero. At the absolute zero, atoms have little kinetic energy as it's possible to get.

Kelvin scale
unit: K
begins at the absolute zero (-273) and so there are no minus numbers

temperature in degrees Celsius = temperature in Kelvin - 273
temperature in Kelvin = temperature in degrees Celsius + 273

The temperature of a gas (in Kelvin) is proportional to the average kinetic energy of its particles

As the kelvin increases, energy increases. As the energy of something increases, its particles will move faster and with more force. This means that more force is exerted over a fixed area increasing the pressure.
So if a gas has its kelvin increased, it will exert more force on its container, and then pressure goes up.

pressure/ temperature (in K) = constant 
p/T = constant 
or: p1/T1 = p2/T2

pressure x volume = constant 
pV = constant 
p1V1 = p2V2 



Tuesday, 24 February 2015

5c) Change of State

Whole Part is for Paper Two ONLY




SOLID LIQUID GAS
regular pattern irregular pattern widely spread
close together random arrangement random arrangement
vibrate move around each other move quickly around in all directions
can't be compressed can't be compressed can be squashed or compressed



Image result for solid liquid gas

5b) Density and Pressure

Density: measure of how 'squashed up' it is
Mass: quantity of matter
Volume: Space occupied by a 3-D object


Density = Mass/Volume

P =  m/v 


unit for density is kg/m3

Experiments to determine density:
Using a set mass of one object change the space its in, then use the formula mass/volume to find density, it will go up as the volume decreases

Pressure: influences upon fluid behaviour

   Image result for pressure trianglePressure = Force/Area 

Pressure difference = height x density x g 

If you have a gas or liquid, it will be exerting an equal pressure in all directions.