ALL OF PHYSICS PAPER 1

• Energy is a number that tells us what will happen when objects interact in a system, and total energy in any interaction is always conserved
• Energy cannot be created or destroyed, but it can be turned into matter (mass).
• Specific heat capacity (shc) tells us how much energy is needed to raise 1kg of a substance by 1°C
• An increase in thermal energy results in particles moving faster, measuring the kinetic energy gained by particles in a substance
• Efficiency is a measure of how much energy going into a system is used usefully, calculated as useful energy out divided by total energy in
• Energy sources are where we harness energy from, including finite (fossil fuels, nuclear fuel) and renewable sources (wind, hydroelectric, solar, geothermal, biofuel)
• Electricity is the flow of charge (electrons) from a source of energy to a component where the energy is released as another type of energy
• In a circuit, the battery has chemical potential energy which is transferred to the electrons, creating a current that flows through the wires
• Potential Difference (PD) or voltage tells us how much energy is transferred per coulomb of electrons passing through a cell or battery
• PD is measured with a voltmeter, always connected in parallel to the components you want to measure the voltage of.
• Current, measured in amps, tells us the rate of flow of charge through a circuit or component
• In a circuit, increasing PD results in a greater current flow, showing that PD and current are directly proportional
• Resistance is measured in ohms, and for a resistor, PD (in volts) equals current (in amps) times resistance (in ohms)
• A resistor has constant resistance, shown by a straight line on a graph of PD against current
• A diode only lets current flow in one direction, with very high resistance in one direction and low resistance in the other
• A thermistor's resistance decreases as temperature increases, opposite to a metal's behavior
• An LDR (light dependent resistor) has resistance that decreases with increased light
• In series circuits, total PD is shared between components, current is the same for all, and total resistance is the sum of all resistances
• In parallel circuits, PD is the same for every branch, current is shared between branches, and adding more resistors in parallel lowers the total resistance
• An LDR is a light dependent resistor similar to a thermistor, but its resistance goes down with increased light intensity, not temperature
• In a circuit on top of a street lamp, as light intensity goes down, the resistance of the LDR goes up, affecting the voltage.
• The neutral wire in a socket stays at a potential of 0 volts, while the Live Wire varies in potential but averages out to an equivalent of 230 volts, known as Main's voltage or Main's PD
• A fuse in a plug, attached to the Live Wire, is designed to melt or blow if the current exceeds a certain number of amps, usually 3, 5, or 13 amps, to prevent damage or harm in case of a current spike
• The National Grid supplies electricity to homes and businesses using a network of power stations and cables to transmit it across the country, with transformers used to step up the transmission voltage to reduce energy loss due to cable resistance
• To find the density of a regular object, calculate its volume using its dimensions, while for an irregular object, use a displacement can to measure the volume of water displaced, indicating the volume of the object
• Solid, liquid, and gas are the three main states of matter, with energy needed to change states supplied as heat to overcome the electrostatic forces of attraction between particles
• During a change of state, particles gain potential energy, not kinetic energy, leading to a constant temperature until the change is complete.
• Heating a gas increases its pressure as the particles gain kinetic energy, move faster, and collide with the container walls more frequently and with greater force, resulting in increased pressure pushing outwards
• Atomic structure:

  • Atoms are made up of positive and negative charges.
  • JJ Thompson discovered the plum pudding model of the atom.
  • Ernest Rutherford found that the positive part of the atom is the nucleus.
  • Nucleus contains protons and neutrons.
  • Electrons exist in shells or orbitals.
  • Different types of atoms are represented by symbols in the periodic table.
  • Atomic number = number of protons in the nucleus.
  • Mass number = protons + neutrons in the nucleus.
  • Isotopes are atoms of the same element with different numbers of neutrons.
• Radiation:

  • Radiation is any particle or wave emitted by something.
  • Electromagnetic spectrum is all radiation emitted by electrons.
  • Gamma radiation is emitted by the nucleus of an atom.
  • Gamma rays are high energy EM waves, can ionize atoms, and are dangerous.
  • Alpha radiation is emitted by nuclei in alpha decay, consists of two protons and two neutrons.
  • Beta radiation is emitted in beta decay, involves a neutron turning into a proton and an electron.
• Radioactivity:

  • Radioactivity is the rate of decay of a source of Alpha, Beta, or Gamma radiation.
  • Radioactivity can be measured in counts per second (Becquerel).
  • Half-life is the time taken for the activity of a source to halve.
  • The half-life of a radioactive isotope can vary from days to millions of years.