Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
X-rays P3.1 Medical scanning P3.2.1-2 Centre of mass and moments Ultrasound Short wavelength Ionising EM wave (transverse) Affect a photographic film in the same way as light Absorbed by metal and bone Transmitted by soft tissue Wavelength roughly same size as an atom Partially reflected when they meet a boundary between Examples include CT scans (3D X-ray), bone fractures, dentalproblems and Examples include pre-natal Centre of mass -the point at which the mass can be thought High frequency sound waves (longitudinal) to be concentrated Above upper limit of human hearing (human hearing T= killing cancer cells s = v x t scanning and the removalof kidney stones pendulum. v = speed (m/s) M=F×d t = time (s) Moment (Nm) = force (N) x perpendicular distance from pivot (m) to halve the time to just and 1 bundle for lighting) Lasers – Used for cutting, cauterising distance to and burning e.g. in eye surgery outside base there is a resultant moment, object will topple of motion (velocity) but not its speed. P3.1 Refraction, lenses and the eye Centripetal force always acts towards centre of the circle. Centripetal force needed increases as: passes from one medium to another. A lens forms an image by refracting light. i = angle of incidence, r = angle of refraction 𝒓𝒆𝒇𝒓𝒂𝒄𝒕𝒊𝒗𝒆 𝒊𝒏𝒅𝒆𝒙 = 𝐬𝐢𝐧 𝒊 𝐬𝐢𝐧 𝒓 Diverging lens (concave) Mass increases Speed increases Radius decreases Triple physics (P3) Refraction-the change of direction of light as it Induction P3.3.2 Transformers If a conductor ‘cuts’ magnetic field lines, p.d. induced across conductor (current flows). If a magnet is moved into a coil of wire, p.d. induced across coil. Alternating current in primary coil Changing magnetic field Applications: - Magnifying glass - Camera The eye - Correction of long sight (eye ball too short) The eye The structure of the eye is limited to: ■retina ■lens ■cornea in iron core Applications: - Correction of short sight (eye ball 𝟏 𝒇 Positive for converging 𝑷 (𝑫, 𝒅𝒊𝒐𝒑𝒕𝒓𝒆𝒔) = Negative for diverging ■pupil /iris ■ciliary muscle ■suspensory ligaments Range of vision (focus): 25cm – infinity Total internal reflection and critical angle 𝟏 𝒓𝒆𝒇𝒓𝒂𝒄𝒕𝒊𝒗𝒆 𝒊𝒏𝒅𝒆𝒙 = 𝐬𝐢𝐧 𝒄 Induces alternating p.d. too long) Lens power Describing images Real – constructed or formed from real light rays Virtual – constructed or formed from virtual/imaginary rays Upright/inverted – right way up/upside down Magnified/ diminished – bigger or smaller 𝒊𝒎𝒂𝒈𝒆 𝒉𝒆𝒊𝒈𝒉𝒕 𝒎𝒂𝒈𝒏𝒊𝒇𝒊𝒄𝒂𝒕𝒊𝒐𝒏 = 𝒐𝒃𝒋𝒆𝒄𝒕 𝒉𝒆𝒊𝒈𝒉𝒕 a Centripetal force -the resultant force causing this acceleration. Load > Force the boundary Converging lens (convex) the centre of the circle. This changes the objects direction Levers Levers act as force multipliers find the v Objects moving in circles continuously accelerate towards For objects not turning (balanced): Total clockwise moment = total anticlockwise moment you might have Contain optical fibres (1 bundle for image P3.2.4 Circular motion Stability -if the line of action of weight is s = distance to boundary (m) *remember 𝐹1 𝐹2 𝐴2 = → 𝐹2 = 𝐹1 → 𝐹2 > 𝐹1 𝐴1 𝐴2 𝐴1 Hydraulics with different areas (e.g. A1 and A2) act as force multipliers. Time period depends on the length of the Moments -the turning effect of a force Endoscopes– Use total internal reflection for imaging. F A Pressure (Pa) = force (N) ÷ area (m2) 1 𝑓 Time period (s) = 1 / frequency (Hz) two different media directions. P= Pendulums 20Hz-20 000Hz) P3.2.3 Hydraulics Liquidsare virtually incompressible, so the pressure is transmitted equally in all across secondary coil Step-up increase p.d. (more turns on secondary coil) Step-down decrease p.d. (fewer turns on secondary coil) 𝑽𝑷 𝒏 𝑷 = 𝑽𝑺 𝒏 𝑺 V = potential difference (V) n = number of turns in coil I = current (A) P = power (W) If transformer is 100% efficient PP = PS so IPVP = ISVS. Switch mode transformers High frequency (50kHz – 200kHz) Lighter and smaller than normal transformers So they are useful for mobile phone chargers etc. Use very little power when no load applied P3.3.1 Motor effect and electromagnets -When a current flows through a wire a magnetic field is produced around the wire. Motor effect If current carrying wire ‘cuts’ through field lines, experiences a force. Size of force increases with: Larger current Stronger magnetic field No force if current parallel to field lines. Electromagnets When current carrying wire coiled around iron, produces an electromagnet. Applications Scrapyard cranes RCCB Bell Fleming’s left hand rule Force is reversed if current or magnetic field changes direction.