Untitled

• Series circuit


  Circuit with only one path for current to flow
• Parallel circuit


  Circuit with multiple paths for current to flow
• In a series circuit, the current is the same through each resistor
• In a parallel circuit, the voltage is the same across each resistor
• Adding resistors in series

  Increases the total resistance, decreases the current
• Adding resistors in parallel

  Decreases the total resistance, increases the current drawn from the battery
• Solving a series circuit

  1. Find total resistance

  2. Use Ohm's law to find current

  3. Calculate voltage drop across each resistor

  4. Calculate power delivered by battery and absorbed by resistors
• Kirchhoff's voltage law


  The sum of the voltage drops around any closed loop is zero
• Power


  The rate of energy transfer, measured in watts (J/s)
• Power = Voltage x Current
• Power = Current^2 x Resistance
• Power = Voltage^2 / Resistance
• Work = Power x Time
• Solving a series circuit with 3 resistors

  1. Find total resistance

  2. Use Ohm's law to find current

  3. Calculate voltage drop across each resistor

  4. Calculate power delivered by battery and absorbed by resistors
• Voltage drops


  The sum of the voltage drops of the resistor must add to the voltage of the battery
• This is in harmony with Kirchhoff's voltage law
• Calculating power delivered by battery and absorbed by resistors

  1. Use V*I for battery

  2. Use I^2*R for resistors
• Power delivered by battery = 360 watts
• Power absorbed by 5 ohm resistor = 180 watts
• Power absorbed by 3 ohm resistor = 108 watts
• Power absorbed by 2 ohm resistor = 72 watts
• Total power delivered by battery = total power absorbed by resistors
• Parallel circuit


  Circuit where current has multiple paths to flow
• Voltage across resistors in parallel is the same
• Calculating current through each resistor in parallel

  Use V=IR for each resistor
• Total current leaving battery = sum of currents through each resistor
• This follows Kirchhoff's current law
• Calculating equivalent resistance of parallel circuit

  1. Use 1/Rtotal = 1/R1 + 1/R2 + ...

  2. Or use Rtotal = V/I
• Equivalent resistance of parallel circuit is less than any individual resistor
• Calculating power delivered by battery and absorbed by resistors in parallel

  1. Use P=VI for battery

  2. Use P=I^2*R for each resistor
• In series, current is the same through all resistors
• In parallel, voltage is the same across all resistors