AQA ENERGY – part 1

1. Energy pathways Change in thermal energy = mass X specific heat capacity X temperature change ∆E= m X cX ∆θ HIGHER: efficiency can be increased using machines. Efficiency = Useful power output Total power input Efficiency = Useful output energy transfer Total input energy transfer Energy stores and changes Energy Conservation and Dissipation AQA ENERGY – part 1 HIGHER: When an object is moved, energy is transferred by doing work. Work done = Force X distance moved Frictional forces cause energy to be transferred as thermal energy. This is wasted. Reducing friction - using wheels, applying lubrication. Reducing air resistance – travelling slowly, streamlining.

2. Power station – NB: You need to understand the principle behind generating electricity. An energy resource is burnt to make steam to drive a turbine which drives the generator. Using renewable energy will need to increase to meet demand. Energy demand is increasing as population increases. Renewable energy makes up about 20% of energy consumption. Fossil fuel reserves are running out. AQA ENERGY – part 2 Using fuels Global Energy Resources National Grid Energy resources

3. Electrons carry current. Electrons are free to move in metal. Series and parallel circuits Circuit symbols Current and Charge Current, potential difference and resistance Controlling current Q = I X t Charge = Current X time R = V X I Energy transfers Power (W) = potential difference X current AQA Electricity Work is done when charge flowing. P = I2 X R Power = (current)2 X resistance E = P X t Energy transferred = Power X time R = V ÷ I Domestic uses and safety Resistance = Potential difference ÷ Current Static electricity PHYSICS only ‘Earthing’ a safety device; Earth wire joins the metal case. Current – Potential difference graphs

4. Pressure of a fixed volume of gas increases as temperature increases (temperature increases, speed increases, collisions occur more frequently and with more force so pressure increases). Temperature of gas is linked to the average kinetic energy of the particles. Kinetic theory of gases Particle model If kinetic energy increases so does the temperature of gas. PV = constant. Pressure No kinetic energy is lost when gas particles collide with each other or the container. P1V1 = P2V2 AQA PARTICLE MODEL OF MATTER Gas particles are in a constant state of random motion. Change in thermal energy = mass X specific heat capacity X temperature change. P = m ÷ V Density = mass ÷ volume. ∆E= m X cX ∆θ Internal energy and energy transfers Change of state Energy needed = mass X specific latent heat. ∆E= m X L

5. Radius of an atom 1 X 10-10m Electrons gained Electrons lost Negative ion Positive ion Atom structure Atoms and Nuclear Radiation Atoms and Isotopes AQA ATOMIC STRUCTURE PHYSICS ONLY: Hazards and uses of Radioactive emissions and of background radiation Discovery of the nucleus Nuclear fission and fusion PHYSICS ONLY: Nuclear energy

6. Each Kg has a gravitational pull of 9.8N. The component forces combined have the same effect. Weight = mass X gravitational field strength W = m X g HIGHER ONLY Gravity Work done against frictional forces, temperature of object rises. Object moves left with a force of 5N Contact and Resultant forces Forces and their interactions If force is at right angles to direction of movement, NO work is done. AQA FORCES – part 1 Work done and energy transfer Scalar and vector quantities PHYSICS ONLY Moments, levers and gears Forces and elasticity Pressure HIGHER ONLY

7. Transverse and Longitudinal waves Energy lost is not at the same rate as energy being absorbed so Earth heats up. Ultraviolet, visible light, infra-red radiation penetrate atmosphere and heat up Earth’s surface. Earth and Global warming Black body radiation Waves in air, fluids and solids In water, use a ripple tank. Properties Measuring speed Longer wavelengths are radiated back, trapped by atmosphere. Sound waves travelling through different mediums, the frequency stay constant. In air, use echoes. AQA Waves e.g. Gamma Angle of incidence = angle of reflection(i) = (r) Short wavelengths have high frequency and high energy. Electromagnetic waves Light refracts as it slows down in a denser substance Magnification = image size ÷ object size HIGHER: Lenses HIGHER: Properties Absorbed light changes into thermal energy store. Seismic waves Air Water Low frequency, long wavelength. EM waves refract High frequency, short wavelength

8. Fleming’s left-hand rule To predict the direction a straight conductor moves in a magnetic field. Right hand rule If current and magnetic field are parallel to each other , no force on wire. F = B X I X l Magnetic field around a wire Force = magnetic flux density X current X length Magnetic fields from the permanent magnet and current in the foil interact. This is called the motor effect. Motor effect HIGHER only Reverse current, magnetic field direction reverses. AQA MAGNETISM AND ELECTROMAGNETISM Reverse the current , foil moves upwards. Further away from the wire, magnetic field is weaker. Aluminium foil placed between two poles of a strong magnet, will move downwards when current flows through the foil. Current large enough, iron filings show circular magnetic field. Induced potential, transformers and National Grid Size of force acting on foil depends on magnetic flux density between poles, size of current, length of foil between poles. Electric current flowing in a wire produces a magnetic field around it. If current is small, magnetic field is very weak. Permanent and Induced Magnetism Magnets PHYSICS HIGHER only Power lost = Potential difference X Current Power supplied to primary coil = power supplied to secondary coil Vp X Ip = Vs X Is Voltage across the coil X number of coils (primary) = Voltage across the coil X number of coils (secondary) Vp ÷ Vs = np ÷ ns

9. Effect of gravity. Gravity causes moons to orbit planets, planets to orbit the Sun, stars to orbit galaxy centres. Too fast = disappears into Space. Correct speed = steady orbit around Earth. Too slow = falls to Earth. Force of gravity changes the moon’s direction not its speed. To calculate speed of Orbit: distance object moves in 1 orbit, Distance = 2∏r, then average speed = distance ÷ time. The life cycle of a star. HIGHER: Circular orbits. Gravity pulls objects towards the ground. Comets, asteroids, satellites. Milky Way our galaxy. Speed of Orbit. Other objects. Orbital motions Solar system Planets close to the Sun, gravity pull is strong. Planets move quickly. Velocity = a vector. AQA SPACE PHYSICS PHYSICS ONLY HIGHER: A planet’s velocity changes but speed remains constant. Planets further away from the Sun, gravity pull is weaker. So speed of planet is slower. Due to the Sun’s gravity, planets accelerate towards the Sun and so changes direction. Frequency of sound wave decreases, wavelength increases. When ambulances go past the sound changes from a high pitch to a low pitch. Red shift Understanding models. Galaxies are moving away from us in all directions. Stars the same size as our Sun. Light from distant galaxies is red-shifted, so galaxy is moving away from us. Galaxies further away have bigger red-shift so are moving faster away. Stars larger than our Sun. Planets and moons moved at different speeds to stars = reason for different positions. OR if collapse is into a really tiny space.