Thermal Physics PDF

Thermal Physics State of matter and its properties Solid Atoms are closely packed together and arranged in order. Atoms can only vibrate or rotate about their fixed position Liquid Atoms are still close to each other. They slide past each other Gas Atoms are far from each other. Move freely and r...

Thermal Physics State of matter and its properties Solid Atoms are closely packed together and arranged in order. Atoms can only vibrate or rotate about their fixed position Liquid Atoms are still close to each other. They slide past each other Gas Atoms are far from each other. Move freely and randomly Solid definite shape and volume Cannot be compressed Liquid takes the shape the container definite volume Gas Volume and size aren’t fixed Easily compressed Change of states Solid -Melting- liquid -Evaporation- Gas Solid -freezing- liquid -condensation- Gas The higher the temperature, the greater the kinetic energy, the faster the motion When temperature is reduced, the average kinetic energy of particles reduces and eventually motion will slow down The temperature at which particle motion seizes or stops is called absoute zero and has a value of -273ºC Force and gas pressure Higher temp, more kinetic energy, atoms bounce more, collides with walls faster, higher pressure When temperature rises, the average speed and kinetic energy of particles rises, the particles will collide more frequently with the walls of the container and so pressure of the gas increases Brownian Motion Suspended particles move rapidly and randomly while colliding and bouncing on air particles Brownian motion is evidence for the kinetic particle model of matter Brownian motions refers to the random movement displayed by small particles that are suspended in liquid or gases. This motion is a result of the collision of particles with other force moving particles in a liquid or gas. Effect on pressure due to a change in temperature When temperature rises, speed of particles increases, if the volume of the gas stays consent its pressure increases because the change of momentum per second when particles collide increases, leading to a larger force per unit area and hence pressure Volume constant, pressure rises Pressure constant, volume rises Increase in pressure = Decrease in volume Decrease volume = increase in pressure P1V1 = P2V2 Specific heat capacity = change in energy/ mass x change in temperature Joules per kgºC Boiling For a pure liquid, boiling occurs at a definite temperature called it's boiling temperature and is accompanied by bubbles that form within the liquid., containing the gaseous or vapour form of the particular substance. Evaporation A few energetic particles close to the surface of a liquid may escape and become gas particles. This process of evaporation occur at all temperatures. Conditions affecting evaporation Higher temperature Larger surface area Wind Cooling by evaporation when evaporation occurs from a liquid and the average kinetic energy of the remaining particle decreases the liquid cools If an object is in contact with the liquid drink evaporation thermal energy will flow from the object to the liquid. The object will cool. It's until it's temperature equals that of the liquid. General properties of waves Transverse waves In a transverse wave, the direction of the disturbance is at the right angles to the direction of propagation of the wave, that is the direction in which the wave travels. Longitudinal waves In a progressive longitudinal wave the particles of the transmitting medium vibrate back-and-forth along the same line as parallel to that in which the wave is travelling Wavelength; the distance between peaks or troughs Frequency; the number of complete waves generated per second the unit is hertz Amplitude; the height of a crest at an undisturbed position Phases; two points which move in the same direction Wave speed the wave is a distance move in the direction of travel of the wave by crest or any point on the wave in one second Speed of wave = frequency x wavelength A wavefront is a line on which the disturbance has the same phase at all points A lined drawn at the right angles to wavefront which shows its direction of travel is called a ray Reflection, reflection, refraction The speed of light is 3x108m/s radio waves, microwaves, infrared light, visible light, ultraviolet light, X-rays, and gamma rays. Lowest to highest frequency. Radio waves - radio and television. Microwaves - satellite communications and cooking food. Infrared - Electrical heaters, cooking food and infrared cameras. Visible light - Fibre optic communications. Ultraviolet - Energy efficient lamps, sun tanning. X-rays - Medical imaging and treatments. Gamma rays - Medical imaging and treatments Speed of wave = frequency x wavelength Reflection of light Reflection of light refers to the bouncing of light when it hits a surface Normal; line is perpendicular to a surface Angle of incidents; angle between incidentally and the normal to a surface Angle of reflection = angle of incidence Reflection of light It refers to the bending of light when he travels from one medium to another The angle of incident is the angle between the instant rate and the normal The angle of refraction is the angle between the refracted rate and the normal A ray of flight is been towards the normal when it goes from less dance to more dense A ray of light bends away from the normal when it goes from more dance to less dense Critical angle At a certain angle of incidents, called the critical angle, the angle of refraction is 90° and the refracted buses along the boundary between the two media Four angles greater than critical angle, the refracted red disappears and all the incident light is reflected inside the dense medium. This is called total internal reflection. Sin I/sin r or 1/sin c Light travels through curve cross road or optical fibre by total internal reflection This is used for endoscopes, telephones, Internet, TV signals and etc Copper cables are more durable and robust Optical fibre cable is cheaper and lighter and easy to install