Physics paper 1 AQA Triple

Exam Tips

• Write with a black pen.
• Stay within the box.
• Use SI units for all calculations.
• Use bullet points for extended response questions.
• Include a conclusion when asked to evaluate.
• Write methods in a numbered list.
• Be confident identifying variables in investigations.
• Understand the difference between repeatable and reproducible results.
• Know that the resolution is the smallest detectable difference in data.
• Recognize that computerized methods are more accurate, sensitive, and rapid.
• Draw lines of best fit correctly.
• Differentiate between systematic and random errors.
• Understand the different metric prefixes and their conversions by factors of a thousand.
• Know that centimeters to meters is converted by a factor of one hundred.
• Use the equation sheet provided, but be prepared to rearrange equations.
• Remember the units for all quantities.

Energy

• A system is an object or a group of objects that can store energy.
• Energy can be stored in different ways, including magnetic, kinetic, thermal, gravitational potential, chemical, elastic potential, electrostatic, and nuclear stores.
• Energy can be transferred between these stores through heating, mechanically, electrically, and by radiation.
• A closed system does not allow matter or energy to enter or leave.
• The law of conservation of energy states that energy cannot be created or destroyed but only transferred.
• Energy is measured in joules (J).

Gravitational potential energy

• Equation: GPE = mgh
• Units:
  • Mass (m) in kilograms (kg)
  • Gravitational field strength (g) in Newtons per kilogram (N/kg)
  • Height (h) in meters (m)
  • GPE in joules (J).

Kinetic energy

• Equation: KE = 1/2mv²
• Units:
  • Mass (m) in kilograms (kg)
  • Velocity (v) in meters per second (m/s)
  • KE in joules (J)

Elastic potential energy

• Equation: EPE = 1/2kx²
• Units:
  • Spring constant (k) in Newtons per meter (N/m)
  • Extension (x) in meters (m)
  • EPE in joules (J)

Specific heat capacity

• Equation: ΔE = mcΔθ
• Units:
  • Change in energy (ΔE) in joules (J)
  • Mass (m) in kilograms (kg)
  • Specific heat capacity (c) in joules per kilogram per degree Celsius (J/kg °C)
  • Change in temperature (Δθ) in degrees Celsius (°C)
• In the specific heat capacity practical, energy is transferred by heating a block of metal or beaker of liquid.
• Key equipment includes a balance, insulation, thermometer, electrical heater, voltmeter, ammeter, stop clock, and joule meter.

Power

• Equation: Power (P) = Energy transferred (E) / Time (t)
• Units:
  • Power (P) in Watts (W)
  • Energy transferred (E) in joules (J)
  • Time (t) in seconds (s)

Efficiency

• Efficiency is the proportion of energy that is usefully transferred.
• It can be expressed as a decimal or a percentage.
• Equations:
  • Efficiency = Useful energy output / Total energy input
  • Efficiency = Useful power output / Total power input
• Energy can be wasted in different ways, most commonly by transferring to the surroundings as thermal energy (heat).
• Wasted energy is described as dissipating.
• To reduce wasted energy:
  • Insulate objects to reduce heat loss.
  • Streamline objects to reduce drag.
  • Reduce friction in systems using wheels or lubrication.

Electricity

• Draw circuit diagrams using a ruler and no gaps.
• Current (I) is the rate of flow of charge in a circuit.
• Potential difference (V) is the difference in electrical potential energy per unit charge between two points in a circuit.
• Conventional current direction is opposite to the actual flow of electrons.

The first electricity required practical

• Measures the IV characteristics of wires of different lengths and resistors in series and parallel.
• Key equipment: ammeter, voltmeter, power pack, and wire.

The second electricity required practical

• Measures current and potential difference across different components, including ohmic conductors, filament bulbs, and diodes.
• Key equipment: ammeter, voltmeter, power pack, and variable resistor.

Ohmic conductors

• Follow Ohm's law (IV = constant).
• Have a linear IV graph that passes through the origin.
• Equation: V = IR
• Units:
  • Voltage (V) in Volts (V)
  • Current (I) in Amps (A)
  • Resistance (R) in Ohms (Ω)

Filament bulbs

• Have a non-linear IV graph that curves upwards.
• Resistance increases as temperature increases.

Diodes

• Only allow current to flow in one direction.
• Have an IV graph that remains horizontal until threshold voltage is reached.

Light-dependent resistors (LDRs)

• Resistance decreases as light intensity increases.

Thermistors

• Resistance decreases as temperature increases.

Series Circuits

• Current is the same everywhere in the circuit.
• Potential difference is shared between components.
• Total resistance (Rt) is the sum of the individual resistances (Rt = R1 + R2 + R3...).

Parallel Circuits

• Current is shared between branches of the circuit.
• Potential difference is the same across each component.
• Total resistance (Rt) is less than the resistance of the smallest individual resistor (1/Rt = 1/R1 + 1/R2 + 1/R3...).

The mains electricity supply

• Alternating current (AC) is used, changing direction 50 times per second.
• Most appliances are connected using a three-core cable with a three-pin plug.
• The three wires are:
  • Live wire (brown) - carries the potential difference.
  • Neutral wire (blue) - completes the circuit.
  • Earth wire (green and yellow stripes) - safety wire.
• Fuses are designed to melt if too much current flows, breaking the circuit.

The National Grid

• A system of cables and transformers that transmits electricity from power stations to consumers.
• Transformers step up the potential difference for efficient transmission and then step it down for safe use in homes.

Static electricity

• Insulating materials become charged when rubbed together due to friction.
• Electrons are transferred, leading to an imbalance of charges.
• Objects with like charges repel, objects with opposite charges attract.
• This is a non-contact force.

Electric fields

• A charged object creates an electric field around itself.
• Electric fields are regions where a charged object would experience a force.
• The force is stronger the closer the object is to the charged object.
• Electric field lines are always drawn from the perspective of a positive charge.
• Lines point away from positive charges and towards negative charges.
• Sparking occurs when charges jump quickly from a charged object to an earthed conductor, discharging it.

Particle Model of Matter

• Matter exists in three states: solids, liquids, and gases.
• The arrangement and movement of particles are different in each state.

Solids

• Particles are closely packed in a regular structure.
• Strong forces hold particles in fixed positions.
• Particles vibrate in fixed positions.
• Solids are difficult to compress.

Liquids

• Particles are closely packed but not in a regular structure.
• Particles can move past one another.
• Liquids can flow and take the shape of their container.
• Liquids are virtually incompressible.

Gases

• Particles are separated by large distances.
• Weak forces of attraction between particles.
• Particles move randomly in all directions.
• Gases can expand to fill any container.
• Gases are easily compressed.

State changes

• Changes in the state of matter occur when particles absorb or release energy.
• Changes in states of matter are physical changes, not chemical changes.
• State changes: melting, freezing, boiling, evaporating, condensing, and sublimation.
• During a state change, energy causes a change in potential energy, not kinetic energy.
• The temperature of a substance remains constant during a state change.

Density

• Density is a measure of mass per unit volume.
• Equation: Density (ρ) = Mass (m) / Volume (V)
• Units:
  • Density (ρ) in kilograms per cubic meter (kg/m³)
  • Mass (m) in kilograms (kg)
  • Volume (V) in cubic meters (m³)

Internal Energy

• The total energy of a system due to particles' kinetic and potential energy.
• Heating a substance increases its internal energy.
• During a state change, internal energy increases potential energy, not kinetic energy.

Specific latent heat

• The amount of energy needed to change the state of one kilogram of a substance.
• Equation: E = ml
• Units:
  • Energy (E) in joules (J)
  • Mass (m) in kilograms (kg)
  • Specific latent heat (l) in joules per kilogram (J/kg)

Pressure and Volume

• Gases have molecules that are constantly in random motion.
• Temperature is a measure of the average kinetic energy of gas molecules.
• At a constant temperature, pressure and volume of a gas are inversely proportional.### Boyle's Law
• The volume of a gas is inversely proportional to the pressure, assuming constant temperature.
• In real-world scenarios, temperature changes influence that relationship, as volume decreases, temperature increases and vice versa.
• For example, pumping up bike tires involves adding energy, which increases kinetic energy of gas molecules.
• This increased kinetic energy results in higher temperature.

Atomic Structure

• The nuclear model of the atom describes a small, dense nucleus containing protons and neutrons, surrounded by electrons in fixed orbits called shells.
• Protons have a relative charge of +1, neutrons have a relative charge of 0, while electrons have a relative charge of -1.
• The relative mass of a proton and neutron is 1, while the mass of an electron is very small.
• The atomic number represents the number of protons, which equals the number of electrons in a neutral atom.
• The mass number represents the total number of protons and neutrons in the nucleus.
• The radius of an atom is about 0.1 nanometers (1 x 10^-10 meters), while the nucleus is only about 1/10,000th of the atom's radius.

Isotopes

• Isotopes are atoms of the same element having the same number of protons but different numbers of neutrons.
• This means they have the same atomic number but different mass numbers.

History of the Atomic Model

• John Dalton proposed atoms as solid, indivisible spheres (like billiard balls).
• J.J. Thomson discovered electrons and proposed the plum pudding model, with negatively charged electrons embedded in a positively charged sphere.
• Ernest Rutherford performed the alpha scattering experiment, which provided evidence for the nuclear model:
  • Most alpha particles passed through a thin gold foil, suggesting the atom is mostly empty space.
  • Some particles were deflected, indicating a small, dense, positively charged nucleus.
• Niels Bohr suggested electrons orbit the nucleus at fixed distances called shells.

Radioactivity

• Some atomic nuclei are unstable and emit radiation as they transition to a more stable state.
• This process is called radioactive decay and happens randomly.
• The rate of decay is called activity, measured in becquerels (Bq) using a Geiger-Müller tube or counter.
• All types of radiation ionize atoms, removing their electrons.

Types of Radioactive Decay

• Alpha Decay: An alpha particle, consisting of two protons and two neutrons (a helium nucleus), is emitted from the parent nucleus, resulting in a daughter nucleus with a different element and a lower mass number.
  • Alpha particles are highly ionizing but have low penetration and a short range in air.
  • Easily stopped by paper.
  • Deflected by electromagnetic fields.
• Beta Decay: A fast-moving electron (beta particle) is emitted from the nucleus.
  • This occurs when a neutron transforms into a proton, releasing an electron.
  • Results in a daughter nucleus with a different element with one more proton.
  • Beta particles are less ionizing than alpha particles but have higher penetration and medium range in air.
  • Stopped by aluminum foil.
  • Deflected by electromagnetic fields in the opposite direction of alpha particles.
• Gamma Radiation: A high-energy, transverse electromagnetic wave emitted simultaneously with alpha or beta decay.
  • Has no effect on element identity or mass number.
  • Low ionizing but highly penetrating, traveling long distances in air and vacuum.
  • Not deflected by electromagnetic fields.
  • Stopped by thick lead.

Radioactive Half-Life

• The half-life is the time it takes for either:
  • The count rate to decrease by half.
  • Half of the atoms in a sample to decay.
• Half-life is constant for a specific radioactive isotope.
• To determine half-life from a graph, find the time it takes for the activity (count rate) to decrease by half.
• To determine half-life from data, repeatedly halve the original activity value, counting the number of steps it takes.

Radioactive Contamination and Irradiation

• Contamination: Occurs when unwanted radioactive atoms become attached to another object. This makes the object radioactive.
• Risk depends on the half-life of the radioactive nuclei and the type of radiation emitted.
• Irradiation: Occurs when an object is exposed to radiation. The object itself does not become radioactive.
• Potential harm arises from ionizing radiation that can damage DNA.

Uses of Radioisotopes

• Radioactive tracers: Used to track the movement of substances within the body.
  • Isotope should have a short half-life, emit beta or gamma radiation, and concentrate in the area of interest.
• Radiation therapy: Gamma radiation targets and destroys cancer cells while minimizing damage to surrounding healthy tissues.
  • Uses focused gamma rays delivered from multiple angles to maximize tumor dose and minimize healthy cell exposure.

Nuclear Fission and Fusion

• Nuclear Fission: Splitting of a large unstable nucleus (like uranium or plutonium) into two smaller nuclei, releasing energy, neutrons, and gamma rays.
  • Induced by neutron bombardment, leading to a chain reaction due to the release of neutrons.
  • Controlled in nuclear reactors for energy generation.
  • Uncontrolled in nuclear weapons and accidents, leading to explosions and meltdowns.
  • Controlled by boron control rods that absorb neutrons.
• Nuclear Fusion: Combining two small nuclei (like hydrogen) into a larger nucleus, releasing even greater energy than fission.
  • Energy release is much higher than fission.
  • Requires extreme temperatures and pressures.
  • Currently not feasible for controlled energy generation on Earth.
  • Used in hydrogen bombs, started by a fission reaction.

Prepare for your physics exam with these essential tips and key concepts regarding energy. Learn the proper techniques for writing your exam, understanding measurements, and addressing common errors. Brush up on the important definitions and rules to set yourself up for success.