topic 12 magnetism

• what can magnets be?

  permanent or induced
• what do permanent magnets do?

  make their own magnetic field.
• what do induced magnets do?

  material that becomes magnetic when put in a magnetic field.
• magnetic materials are always attracted to magnets what are they?

  iron, steel, cobalt and nickel.
• what happens if magnetic materials removed from magnetic field?

  loses its magnetism
• Permanent magnet uses:

  • creating objects that are designed to stick to other objects.
  • fridge magnets
  • compass
• induced magnet uses

  • useful if you want permanent magnets to stick to them.
  •  magnetic noticeboard 
•  uniform magnetic field.?

  All the field lines are evenly concentrated, so the magnetic field has the same strength everywhere between the magnets.
• The field lines between 2 parallel magnetic poles are...

  parallel
• arrows on magnetic field point from

  north to south
• Plotting compass uses?

  to draw the field lines of a magnetic field.
• why is earth north pole actually the south pole?

  Compasses point to the North Pole because they are attracted to the south pole of the Earth's magnet.
• what is the earth core made up of that suggests its a magnet?

  Iron and nickel.
• (electromagnet)When a current flows through a long, straight wire it produces what?

  magnetic field around wire
• larger current = stronger magnetic field
• right hand grip rule

  • thumb = direction of current
  • gripped fingers = magnetic field direction
• weaker = field lines further apart
• electromagnet field is?

  circular
• how do you reverse direction of electromagnetic field

  reverse current
• what is a solenoid(electromagnet)?

  coil of wire with current flowing through it has same shape of field as bar magnet
• solenoid: the field in the coil is uniform meaning?

  same strength and direction
• How do we know the field outside the coil is non-uniform(solenoid)

  points in different direction sand has different size at all points
• why is magnetic field disappearing around electromagnet when current is switched off a good thing?

  you can turn it on and off
• Too increase strength of electromagnet:

  • add more coils of
  • increase current
  • add iron core
• Inside a solenoid, the field lines from the individual coils point in  same direction so ?

  The  fields add together, which increases the strength of the magnetic field inside the solenoid.
• Outside a solenoid, the field lines from individual coils point in opposite directions so?

  The fields cancel out, which decreases the strength of the magnetic field outside the solenoid.
• motor effect

  • 2 magnetic fields occupy same space they exert equal and opposite forces on each other because a current carrying wire is placed between poles of horseshoe magnet so wire experiences a force at 90 too field and current
• What is iron filling used for?

  To show shape of magnetic field
• Magnetic materials that gain and lose magnetism quickly are called ?

  magnetically soft materials.
• Magnetic materials that gain and lose magnetism slowly are called ?

  magnetically hard materials
• In the right hand rule, the thumb is placed following the same direction as the current is travelling, and the fingers are the curled in the direction of the magnetic field lines