physics - pressure

• Calculating the pressure of a fluid acting at a surface

  1. Force of fluid normal to surface

  2. Divide by area of surface

  3. Pressure in Pascals
• Atmospheric pressure


  Decreases with increase in height
• Gases


  • Particles are widely spaced, unmoving, rapidly colliding with each other and walls
• Liquids


  • Particles exerting force normal to walls of container
• Fluids


  Gases and liquids
• Atmospheric pressure at surface

  Greatest number of air molecules in given volume
• Atmospheric pressure with height

  Decreases as number of air molecules above surface decreases
• Mountain climbers take oxygen supply due to low air pressure
• The SI unit of pressure is pascal (Pa).
• What is the phenomenon of electromagnetism?

  It is the phenomenon whereby electric currents produce their own magnetic fields.
• How do electric currents affect magnetic fields in wires?

  Electric currents produce their own magnetic fields around the wires.
• What shape do the magnetic field lines take around a wire with current flowing through it?

  The magnetic field lines are concentric circles around the wire.
• Where is the magnetic field strongest around a wire?

  The magnetic field is strongest closest to the wire.
• What determines the direction of the magnetic field around a wire?

  The direction of the magnetic field depends on the direction of the current.
• How can you remember the direction of the magnetic field using your hand?

  You can use the right hand rule by curling your fingers in the direction of the field and pointing your thumb in the direction of the current.
• What is the direction of the magnetic field when the current flows upwards in a wire?

  The magnetic field would be going anti-clockwise around the wire.
• What happens to the magnetic field when the current direction in a wire is reversed?

  The direction of the magnetic field also reverses.
• What occurs when two wires with currents in opposite directions are joined together?

  The magnetic fields will interact and form a single magnetic field through the center of the coil.
• What is a solenoid?

  A solenoid is a long piece of wire coiled into a series of turns.
• How does the magnetic field within a solenoid compare to that of a bar magnet?

  The magnetic field within a solenoid is strong and uniform, similar to that of a bar magnet.
• What do we call a magnet created by electricity?

  An electromagnet.
• What happens to an electromagnet when the current is turned off?

  The magnetic field disappears when the current is turned off.
• How can the direction of the magnetic field in an electromagnet be reversed?

  By reversing the direction of the current flowing through the wire.
• What are the four ways to increase the strength of an electromagnet?

  Increase current, increase number of turns, decrease length of coil, and add an iron core.
• Why does adding an iron core to a solenoid increase its strength?

  Iron is a soft magnetic material that becomes an induced magnet when the solenoid is switched on.
• What happens to the iron core when the current is turned off?

  The iron core loses its magnetic field when the current is turned off.