Knowt
Physics 21st Century (OCR)
1. Energy
Energy Forms and Transfers:
Mechanical Energy: Includes both kinetic energy (energy of motion) and potential energy (energy stored in an object due to its position or state). For example, a falling rock has potential energy at the top that converts to kinetic energy as it falls.
Thermal Energy: This is the energy of particles in motion. The faster the particles move, the more thermal energy they have, and this is linked to temperature.
Chemical Energy: Stored in chemical bonds and released during chemical reactions. For instance, the energy stored in fossil fuels is released when burned.
Nuclear Energy: Energy released during nuclear reactions, such as nuclear fission (splitting atoms) and nuclear fusion (combining atoms).
Renewable vs Non-renewable Energy:
Hydropower: Using water to generate energy, often through dams. While renewable, its environmental impact includes ecosystem disruption.
Wind Energy: Wind turbines convert the movement of air into electrical energy. Countries like Denmark have become leaders in wind power production.
Solar Energy: Solar panels harness sunlight and convert it into electricity. Solar power is a rapidly growing sector, and improvements in solar cell efficiency (e.g., perovskite solar cells) are making it more viable.
Energy Storage:
Modern energy storage solutions like lithium-ion batteries and flow batteries are essential for balancing the supply of intermittent renewable energy, such as solar or wind, ensuring that power is available even when the sun doesn’t shine or the wind doesn’t blow.
2. Electricity and Magnetism
Ohm's Law (V = IR):
Resistors: Components used to control current in circuits. Resistors are crucial in electronics for creating specific voltages or currents and have applications in almost all electrical devices.
Superconductivity: A phenomenon where certain materials, when cooled to very low temperatures, have zero electrical resistance. This could lead to more efficient power transmission and even magnetic levitation systems (like Maglev trains).
Electromagnetic Induction:
Induction Cooking: Induction cooktops use electromagnetic induction to directly heat pots and pans, making cooking faster and more energy-efficient.
Transformers: These devices use electromagnetic induction to increase or decrease the voltage in alternating current (AC) circuits. This is critical for the distribution of electricity across long distances with minimal energy loss.
Electric Motors: Electric motors use electromagnetism to convert electrical energy into mechanical energy. Modern electric vehicles (EVs) and many home appliances rely on electric motors.
Magnetic Fields:
Electromagnets: An electromagnet uses electricity to generate a magnetic field, which can be turned on and off. They’re used in everything from MRI machines to junkyard cranes.
Magnetism and Communication: Magnetic fields are essential in technologies like hard drives (storing data) and magnetic resonance imaging (MRI) for medical scans.
3. Forces and Motion
Newton’s Laws of Motion:
Applications in Transportation: Understanding forces and motion helps engineers design safer and more efficient vehicles. For example, crumple zones in cars use the concept of force distribution to minimize the impact during a collision.
Rockets and Space Exploration: The third law of motion (action and reaction) is crucial for understanding how rockets work. The exhaust gases expelled from a rocket push the rocket forward into space, allowing it to break free of Earth’s gravity.
Forces and Acceleration (F = ma):
Space Travel: The force needed to accelerate spacecraft is determined by this equation. Rocket scientists calculate the exact force needed to achieve escape velocity to leave Earth’s atmosphere and enter orbit.
Accelerators: Particle accelerators like the Large Hadron Collider (LHC) use intense forces to accelerate particles close to the speed of light, enabling scientists to study subatomic particles.
Momentum:
Sports: Understanding momentum is key in sports like football and car racing, where athletes and vehicles need to control their momentum to move efficiently or avoid collisions.
Space Physics: Momentum is conserved in space, so spacecraft can perform complex maneuvers without using extra fuel by exploiting gravitational slingshot effects from planets and moons.
Gravitational Forces:
Satellites and Orbits: Satellites orbit Earth due to the gravitational pull of Earth, balancing the centrifugal force from their motion. Engineers calculate the exact speed and altitude needed to keep satellites in geostationary orbit.
Black Holes: A region in space where gravity is so strong that nothing, not even light, can escape. Understanding black holes is helping scientists probe the limits of general relativity.
4. Waves
Electromagnetic Spectrum:
Radio Waves: Used in communication (radio, TV, mobile networks) and radar. Advances in 5G wireless technology use high-frequency radio waves to provide faster internet speeds.
Microwaves: Used for cooking and also in satellite communications and radar. Some radar systems use microwave radiation to detect objects and measure distances.
Gamma Rays: Employed in medical applications for cancer treatment (radiotherapy) and for detecting the most energetic objects in the universe (like black holes and neutron stars).
Reflection, Refraction, and Diffraction:
Optical Fibers: These use the principle of total internal reflection to transmit light signals over long distances with minimal loss. Fiber optic cables are integral to the internet, enabling high-speed data transfer.
Lenses and Telescopes: Refraction allows light to bend through lenses, forming images. Telescopes use large lenses to collect light from distant stars, helping us understand the universe’s structure.
5. Modern Physics
Quantum Theory:
Superposition: This principle, which says that particles can exist in multiple states at once, is the foundation of quantum computing. A quantum computer uses qubits, which can represent both 0 and 1 at the same time, offering immense processing power.
Entanglement: This phenomenon occurs when two particles become linked in such a way that the state of one instantly affects the other, regardless of distance. This concept is used in quantum encryption to create unbreakable codes.
Nuclear Physics:
Fission: In nuclear power plants, uranium atoms are split to release energy. However, fission has waste products, which pose environmental concerns. Research into better nuclear waste disposal methods and more efficient reactors (like thorium reactors) is ongoing.
Fusion: Fusion is the process that powers the sun. Scientists are working on creating fusion reactors that could provide virtually unlimited energy without the harmful waste associated with fission. Projects like ITER in France aim to make fusion energy a reality.
Particle Physics:
The Standard Model: The theory that describes the fundamental particles (quarks, leptons, and bosons) and their interactions. Discovering the Higgs boson at the LHC confirmed the existence of the Higgs field, explaining why particles have mass.
Dark Matter and Dark Energy: These unknown substances make up most of the universe’s mass and energy. Dark matter interacts with normal matter via gravity, while dark energy is driving the accelerated expansion of the universe.
6. Space Physics
Space Exploration:
Human Spaceflight: Agencies like NASA, ESA, and private companies like SpaceX are working on human missions to Mars and beyond. SpaceX’s Starship is being designed to carry humans to Mars, and NASA’s Artemis program aims to land the first woman and next man on the Moon by 2024.
Robotic Missions: Robotic spacecraft like NASA's Perseverance rover on Mars are revolutionizing our understanding of the solar system by gathering data from planets, moons, and asteroids.
Satellite Technology:
GPS: Global Positioning System satellites provide real-time location data using signals from multiple satellites in orbit. GPS is essential for navigation, from everyday travel to military operations.
Weather Satellites: Satellites like NOAA’s GOES series track weather patterns, including storms and hurricanes, providing vital data for forecasting.
Cosmology and the Big Bang:
Cosmic Microwave Background: The CMB is the afterglow of the Big Bang, offering insights into the early universe's conditions. Telescopes like the Planck satellite study the CMB to understand the universe's expansion and composition.
Exoplanets: The discovery of thousands of exoplanets (planets outside our solar system) is reshaping our understanding of planetary formation and the potential for life elsewhere. Space telescopes like Kepler and TESS search for Earth-like exoplanets in the habitable zone.
