practical 10 - magnetic force on a wire

• equipment

  • wire to suspend
  • two stands with clamps
  • two identical magnets
  • weighing scales
  • ammeter
  • variable power supply
  • ruler
• method

  • set up apparatus
  • measure and record the length of the magnets
  • zero balance with no current flowing
  • adjust voltage so current is 0.5A
  • read and record mass on balance
  • increase voltage so current increases by 0.5A and repeat increasing by 0.5A to 6A
  • repeat experiment twice more and record mean mass for each current
• graphs and calculations

  • calculate force
  • convert mass to kg and multiply by 9.81
  • plot graph of force against current and draw line of best fit
  • magnetic field strength = gradient divided by the length
  • $F=$$BIL\ \ \rightarrow\ \ B=$$\frac{F}{IL}=$$\frac{G}{L}$
• safety

  • wire could overheat and burn

  precautions

  • don't touch the wire
• improvements

  • variable reisitor can be added in series to make it easier to get desired currents
  • use scales with very high resolution because forces are small