equations

• wavespeed = frequency x wavelength


  $v =$$fλ$
• energy transferred = power x time


  $E =$$Pt$
• efficiency

  useful energy transferred / total energy transferred
• Charge = current x time


  $Q =$$It$
• Potential difference = current x resistance


  $V =$$IR$
• Potential difference = work done (energy transferred) / charge


  $V =$$E/Q$
• power = energy / time


  $P =$$E/t$
• Energy transferred (work done) = charge flow x potential difference


  $E =$$QV$
• Power = Potential difference x current


  $P =$$IV$
• power = (current)^2 x resistance


  $P =$$I^2R$
• force = magnetic flux density x current x length of conductor


  $F =$$BIl$
• potential difference across primary coil x current in primary coil = potential difference across secondary coil x current in secondary coil


  $VpIp =$$VsIs$
• potential difference across primary coil / potential difference across secondary coil = number of turns in primary coil / number of turns in secondary coil


  $Vp / Vs =$$Np / Ns$