physics 1

• objects normally have a neutral charge overall, explain why


  objects consist of atoms which consist of protons, neutrons and electrons

  normally, the number of positive protons is equal to the number of negative electrons, so the overall charge is neutral
• if an object has a strong enough charge, what can it do to the surrounding air?


  it can ionise the air

  this means it causes the particles in the air to lose electrons so that they become charged

  the air is then able to conduct electricity
• what does a diode do?

  diodes only allow current to flow one way around a circuit
• what happens to resistance in a parallel circuit

  the more loops you have in a parallel circuit, the lower the total resistance will be

  this is true regardless of the resistance of each component
• what is Ohm's law?


  Ohm's law describes the relationship between voltage, current and resistance: V=IR
• what does a step-up transformer do?


  increase the voltage and decrease the current of electricity
• how does a fuse work?

  fuses have a thin wire which melts and breaks the circuit when the current is too high

  the rating of a fuse is the current that will cause the fuse to break the circuit
• earth wire colour?

  stripey green and yellow
• what are the units of charge?

  coulombs (C)
• disadvantage of a series circuit


  if any single component breaks, the whole circuit will not function
• parallel circuit?


  a circuit in which each component has its own loop
• what is wrapped around each wire and why?

  plastic

  used as an insulator and humans can handle it without getting electrocuted
• mains electricity?

  electricity generated by power stations and delivered to homes via the national grid - wall sockets
• how do earth wires prevent electric shocks?

  connected to the casing of the appliance, if the live wire touches the appliance casing, the earth wire provides an alternative pathway for electricity to flow
• what happens to potential difference in a series circuit?


  it is shared across all the components
• when two materials are rubbed together, which particles are transferred?


  electrons !
• how do circuit breakers work?

  act like a switch that will open when there is a surge in current

  they can be reset electrically, rather than having to be replaced
• resistance

  everything that resists or opposed the flow of electrons in a circuit
• fixed resistor?

  has a fixed resistance that cannot be changed
• how is hydroelectricity generated?

  1. as water flows downhill, a hydroelectric dam will trap the water in a reservoir
  2. whenever water is released through the dam, it spins turbines which are connected to generators, and so produces electricity
  3. the water can then return to the river on the lower side of the dam
• as an object falls, which energy stores does energy pass between?

  grav potential ---> kinetic energy
• work done?

  energy transfer that occurs when a force is used to move an object by a certain distance
• wave power

  the water in the sea rises and falls because of waves on the surface

  wave machines use the kinetic energy of this motion to drive electricity generators
• power?

  work done over time / rate at which energy is transferred
• energy transfers

  mechanically

  electrically

  by heating

  by radiation

  via light

  sound waves
• conservation of energy law

  energy cannot be created or destroyed, only transferred from energy stores or dissipated
• 8 energy stores

  kinetic

  gravitational potential

  elastic potential

  thermal

  nuclear

  magnetic

  electrostatic

  chemical
• two factors that affect the strength of gravitational attraction between two objects

  distance between them

  mass of each object
• gravitational potential energy?

  energy an object has due to its height in a gravitational field
• thermal energy store (internal energy)


  how much energy a substance has, it includes two stores of energy:

  1. kinetic energy store
  2. potential energy store
• steps of convection

  first

  1. as the fluid is heated, the particles gain kinetic energy and spread apart
  2. the heated fluid is less dense, it rises above cooler fluid
  3. as it cools down, it becomes more dense again and sinks
  4. as it occurs in a limited space such as a container, it creates convection currents
• 3 disadvantages of hydroelectricity

  ....

  1. large environmental impact on the area upstream, as the reservoir can disrupt natural habitats
  2. expensive to build initially
  3. only possible in regions with the right kinds of rivers
• state(s) of conduction

  soild
• 3 advantages that wind and solar have in common

  ....

  1. renewable
  2. cheap to run once set up
  3. dont do any permanent damage to the environment or release pollutants
• reduce friction between bike chain and bike cogs?

  lubricant, e.g. oil
• how do tidal barrages generate electricity?

  ....

  1. as tide comes in, a tidal dam will trap the water upstream
  2. once the tide has gone back out, water is released through the dam which spins turbines connected to generators and produces electricity
  3. water can then return to the river on the lower side of the tidal barrage
• how is bio fuel different to a fossil fuel e.g. petrol

  bio fuels are made from living or recently living organisms such as plants or algae or animal waste

  fossil fuels are made from organisms which died millions of years ago
• for radioactive substances inside the body, which type of radiation is most harmful? explain

  alpha radiation , most ionising so damages our cells the most