Hoja de repaso: Fundamentals of Physics and Nuclear Science

📋 Course Outline

1. Energy stores, transfers and equations
2. Electricity, circuits and mains power
3. Particle model and density
4. Atomic structure and nuclear radiation

📖 1. Energy stores, transfers and equations

🔑 Key Concepts & Definitions

• Kinetic energy : Kinetic energy is the energy a moving object has due to its speed.
• Gravitational potential energy : Gravitational potential energy is the energy an object has because of its height in a gravitational field.
• Thermal energy transfer : Thermal energy transfer is energy moved because of a temperature difference, often described using heating equations.
• Efficiency : Efficiency is the fraction of total energy input that becomes useful output energy.

📝 Essential Points

• Kinetic energy is given by $KE=\tfrac{1}{2}mv^2$ where $m$ is mass and $v$ is speed.
• Gravitational potential energy changes with height as $GPE=mgh$ where $g$ is gravitational field strength.
• Specific heat capacity links energy transfer to temperature rise using $\Delta E=mc\Delta\theta$.
• Latent heat uses $\Delta E=mL$ for the energy transferred during a change of state.
• Electric and nuclear energy are transferred via electricity and radiation, respectively, while mechanical transfer and heating also occur.
• Efficiency is calculated as useful energy divided by total energy, matching the exam equation form useful/total.

💡 Memory Hook

KE grows with $v^2$; if speed doubles, kinetic energy becomes 4×.

📖 2. Electricity, circuits and mains power

🔑 Key Concepts & Definitions

• Series circuit : A series circuit is wired so components share the same current along the circuit.
• Parallel circuit : A parallel circuit is wired so each branch has the same voltage across it while current splits.
• UK mains power : UK mains power refers to the standard household supply with specified voltage and frequency plus colour-coded conductors.
• Electric power equation : Electric power is the rate of energy transfer and can be related to current, voltage, and time.

📝 Essential Points

• In a series circuit, the current is the same everywhere and the voltages add across components.
• In a parallel circuit, the voltage is the same everywhere while current splits between branches.
• UK mains values are 230 V and 50 Hz, with live brown, neutral blue, and earth green/yellow.
• Ohm’s law uses $V=IR$ to link voltage, current, and resistance.
• Power equations include $P=VI$, $P=I^2R$, and energy transfer $E=Pt$ when power acts for a time $t$.
• Practical I–V characteristics distinguish a resistor as a straight line from a bulb as a curve and a diode as one-way.

💡 Memory Hook

Series: same I; Parallel: same V.

📖 3. Particle model and density

🔑 Key Concepts & Definitions

• Density : Density is the mass per unit volume of a material.
• Particle model : The particle model treats matter as particles whose motion and spacing explain properties like pressure and density.
• Gas pressure-volume relationship : The gas pressure-volume relationship links $P$ and $V$ for a gas at constant temperature using an equation.

📝 Essential Points

• Density is calculated using $\rho=\tfrac{m}{V}$ where $\rho$ is density, $m$ is mass, and $V$ is volume.
• For a gas at constant temperature, pressure and volume obey $P_1V_1=P_2V_2$.
• Density practical uses mass and volume to determine $\rho$ via mass/volume.
• To find SHC, use an insulated block with a heater and thermometer to measure temperature rise.
• To measure resistance, vary wire length and use $V/I$ data to infer resistance from the circuit readings.
• Required resistance practical uses changing length (and corresponding readings) to build the relationship between resistance and wire properties.

💡 Memory Hook

Density is mass over volume: $\rho=m/V$.

📖 4. Atomic structure and nuclear radiation

🔑 Key Concepts & Definitions

• Atomic number : Atomic number is the number of protons in an atom’s nucleus.
• Isotopes : Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons.
• Half-life : Half-life is the time taken for half of the unstable nuclei in a sample to decay.
• Nuclear radiation types : Nuclear radiation types describe different kinds of emissions from the nucleus: alpha, beta, and gamma.

📝 Essential Points

• A proton has charge +1, a neutron has charge 0, and an electron has charge −1.
• Isotopes share the same number of protons but differ in their number of neutrons.
• Alpha radiation is most ionising and is stopped by paper, with alpha described as a helium nucleus.
• Beta radiation is stopped by aluminium and is described as an electron.
• Gamma radiation is the least ionising and is stopped by lead, and it is an electromagnetic wave.
• Fission splits uranium in a chain reaction for nuclear power, while fusion joins hydrogen in stars.

💡 Memory Hook

Alpha: paper, most ionising; Beta: aluminium; Gamma: lead, least ionising.

📊 Synthesis Tables

Circuit comparisons

Circuit type	Current	Voltage
Series	Same everywhere	Shared and adds
Parallel	Splits between branches	Same everywhere

⚠️ Common Pitfalls & Confusions

1. Mixing up the circuit rules by swapping series and parallel statements about current and voltage.
2. Forgetting to use $v^2$ in $KE=\tfrac{1}{2}mv^2$, leading to wrong scaling when speed changes.
3. Using $mL$ for anything other than latent heat or a state change, or using $mc\Delta\theta$ when there is no temperature change.
4. Confusing energy transfer with power by using $E=Pt$ incorrectly when time is not included.
5. Thinking isotopes differ in proton number rather than in neutron number.
6. Mixing radiation types and shields, especially which is stopped by paper versus aluminium versus lead.

✅ Exam Checklist

1. Match each energy transfer type to the correct equation, including $KE=\tfrac{1}{2}mv^2$, $GPE=mgh$, $\Delta E=mc\Delta\theta$, and $\Delta E=mL$.
2. Calculate efficiency as useful/total and interpret it as a fraction of input energy that becomes useful output.
3. For series circuits, state that current is the same everywhere and total voltage is shared across components.
4. For parallel circuits, state that voltage is the same everywhere and current splits between branches.
5. Use UK mains facts to identify live (brown), neutral (blue), and earth (green/yellow) together with 230 V and 50 Hz.
6. Apply $V=IR$ and the power relations $P=VI$ and $P=I^2R$ to solve circuit questions with correct quantities.
7. Use $E=Pt$ to connect power, time, and energy transfer in electricity calculations.
8. Compute density using $\rho=\tfrac{m}{V}$ and describe how the density practical uses mass and volume.
9. Use $P_1V_1=P_2V_2$ for gases only when temperature is constant.
10. State the charges of proton (+1), neutron (0), and electron (−1) and use them to identify nuclear composition.
11. Distinguish isotopes by having the same protons and different neutrons.
12. Recall alpha (paper, most ionising), beta (aluminium), and gamma (lead, least ionising) plus their basic descriptions.
13. Use the half-life definition to explain what “half the nuclei have decayed” means.
14. Explain that fission splits uranium in a chain reaction for nuclear power and fusion joins hydrogen in stars.