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• Why does the movement of the bar magnet induce a potential difference across the coil?

  the magnetic field (lines) cut by the coil

  Why is the induced potential difference across the coil alternating?

  magnet changes direction
• The further a swimmer dives below the surface of the sea, the greater the pressure on the swimmer

  • increasing depth increases the mass / volume (of the water column) above the swimmer
  • increasing the weight / force (of water) acting on the swimmer
• Explain why the velocity of the satellite changes as it orbits the Earth

  • force of) gravity causes the satellite to accelerate (towards the Earth)
  • the acceleration causes a change in direction velocity
  • changes because direction changes
• Explain why refraction happens at the boundary between the deep water and shallower water.

  • velocity / speed is slower in shallow water
  • so edge of wave (front) entering shallow water slows down
  • one part of the wave (front) changes speed before other parts
• Explain why the wave fronts in Figure 17 do not refract at the boundary.

  • every point on the wave hits the shallow water at the same time
  • every point slows down at the same time
• MOTOR EFFECT

  • the sides of the coil experience a force
  • moments cause the coil to rotate (clockwise / anticlockwise)
  • the two halves of the (rotating) commutator swap from one brush to the other
  • keeping the forces in the same direction (keeping the coil rotating
• Explain the factors that affect the distance needed to stop a vehicle in an emergency

  • reaction time explained in terms of longer reaction times increase thinking distance (from a given speed), drinking alcohol, tiredness, distractions
  • increased speed increases KE so increases work done to stop the vehicle,
  • condition of the tyres, condition of road surface • wet/icy roads explained in terms of condition of tyres and road surface (including weather considerations) affecting friction (between tyres and road)
• brakes overheating or brakes locking (causing) loss of control
• The term red-shift describes the observed increase in the wavelight of the light from a distant galaxy
• the universe began from a very small region

  • furthest galaxies are moving the fastest
• MOTION

  • initially air resistance is less than weight / gravity
  • so the skydiver accelerates acceleration causes the air resistance to increase
  • resultant force decreases to zero
  • so the skydiver falls at terminal velocity
• Explain how a moving-coil microphone works

  • sound (waves) cause the diaphragm to vibrate
  • the diaphragm causes the coil / wire to vibrate
  • the coil / wire moves through the magnetic field
  • a potential difference is induced (across the ends of the coi