resistance and v=ir

• potential difference formula


  potential difference=current x resistance
• potential difference units


  volts
• current units


  amps
• resistance units


  ohms
• resistance depends on


  series circuit

  parallel circuit

  length of wire
• resistance practical

  attach a crocodile clip to a wire at ocm on the ruler

  attach second one 10cm away

  close switch and record current and pd

  open switch and move second clip and record new length, current and pd

  repeat

  calculate resistance

  plot a resistance and wire length graph
• independent variable


  length of wire
• dependent variable


  resistance of the wire
• control variable


  thickness of the wire, material of the wire, temperature of the wire
• aim

  how does length of wire affect resistance
• method


  set up circuit

  connect 10 cm of wire

  record pd and current

  calculate resistance

  repeat for various length

  plot resistance against length on a graph