Physics: equations

• Current: $I =$$Q/T$
• Resistance: R = V/I
• Resistance = voltage/ current
• Current = charge / time
• The total resistance in a series circuit is equal to the sum of the resistance at each component.
• Total resistance, R total = r1 + r2
• The total current through the whole circuit is the sum of the currents through each component.
• In a series circuit, the same current passes through each component
• For components in parallel, the potential difference across each component is the same.
• Oscilloscope:

  frequency = 1/time taken for one cycle

  voltage = voltage(y)division x the number of squares it goes up

  period: work out using the given timebase x how many squares one whole cycle is
• 
  

  power = energy/ time
• Energy = power x time
• power = current x potential difference
• Resistance heating: power supplied to resistor

  $Power =$$i^2r$
• Charge flow:

  Charge = current x time

  $Q =$$It$
• When charge flows through a resistor, energy is transferred to the resistor, so it becomes hotter
• Energy transferred to a component:

  energy = voltage x charge

  $E =$$VQ$
• efficiency = output power/ input power (x100)
• output power = efficiency x input power
• Potential difference across a component:

  Potential difference = energy transferred/ Charge

  $P.D. =$$E/Q$