physics paper 1

• Kinetic energy equation


  E = 1/2 mv^2
• Rearranging kinetic energy equation


  V = √(2E/m)
• Gravitational potential energy equation

  GPE = mgh
• Power


  The rate of energy transferred or rate of work done
• Efficiency


  Useful energy out / Total energy in
• Current equation


  I = Q/t
• Units of current and charge

  Current (I) in Amperes (A), Charge (Q) in Coulombs (C)
• Ohm's Law


  V = IR
• Resistance of filament bulb increases with current due to increased collisions with hot ions
• Components in series


  • Same current, PD shared based on resistance
• Components in parallel


  • Same PD, current shared
• Thermistor


  Resistor whose resistance decreases with increasing temperature
• LDR


  Light dependent resistor, resistance decreases with increasing light intensity
• UK mains electricity


  230V, 50Hz AC
• Step-up transformer


  Increases voltage to reduce current and power losses in transmission
• Step-down transformer


  Decreases voltage to 230V for household use
• Positive charge at the center of the electric field
• Finding density of regular and irregular objects

  Regular: Volume = length * width * height

  Irregular: Volume = water displaced
• Internal energy


  Sum of kinetic and potential energies of particles
• Temperature stays constant during melting/evaporation as energy is used to overcome particle attractions
• Ways to increase gas pressure

  • Decrease volume, add more gas, increase temperature
• Pressure and volume are inversely proportional for a gas at constant temperature (Boyle's Law)
• Rutherford discovered the atom has a small positive charge at the center (the nucleus)
• Alpha, beta, gamma radiation

  Alpha: Helium nuclei, stopped by paper

  Beta: High energy electrons, stopped by aluminium

  Gamma: High energy EM waves, reduced by lead/concrete
• Sources of background radiation

  • Cosmic rays, radon gas, medical equipment, nuclear weapons, some foods
• Energy in nuclear fission and fusion comes from the decrease in mass of the nuclear fuel