Germany Jahrgangsstufe 8 Physics
Chapters: 4
1. Electric current
Electric Current
- Electric Current, Potential Difference and Electric Circuits – Electric current is the rate of flow of charge, I = Q/t, measured in amperes with an ammeter joined in series. Potential difference is the work done to move a unit charge between two points, V = W/Q, measured in volts with a voltmeter joined in parallel. Charge flows only in a closed circuit.
2. Optics
Optics
- Refraction of Light: Laws, Refractive Index and the Glass Slab – Light changes speed when it goes from one transparent medium to another, and so it bends at the boundary (unless it hits along the normal). Going into an optically denser medium it slows down and bends toward the normal; coming out it speeds up and bends away. For a pair of media, sin i / sin r stays constant (Snell's law); this constant is the refractive index, which also equals the ratio of the speeds of light, n = c/v. In a rectangular glass slab the emergent ray is parallel to the incident ray but shifted sideways (lateral displacement).
3. Mechanics
Dynamics of 2D Motion · Forces and Their Effects
- Force and Laws of Motion – A force is a push or a pull. Balanced forces (net force zero) do not change motion; an unbalanced force changes speed or direction. Friction opposes sliding. First law: a body keeps its state of rest or uniform motion unless an unbalanced force acts (inertia; heavier bodies have more inertia). Momentum p = mv. Second law: F = ma (rate of change of momentum), 1 N = 1 kg m/s². Third law: forces come in equal and opposite pairs acting on two different bodies. For a system with no outside force, internal forces cancel and total momentum is conserved.
4. Profile area (science-technology school)
Solar Cells and Other Power Sources · Physics Practical Projects
- Minerals and Energy Resources – Minerals are natural substances found in rocks. They are metallic (ferrous or non-ferrous), non-metallic, or energy minerals. Energy comes from conventional sources like coal, petroleum, natural gas and electricity, and from non-conventional sources like sun, wind, nuclear, biogas, tides and heat from the Earth. Both minerals and energy must be conserved.
- The Scientific Method – The scientific method is the careful way scientists find out how the world works. Observe something, ask a testable question, make a hypothesis (a clear, testable guess), test it with a fair experiment (change one variable, measure one, keep the rest the same), repeat and record data, analyse it, draw a conclusion and share it so others can check. Results that fail the test are useful too: they send you back to a new hypothesis.