Blog 5: Resistance --- Ohm's Law

Section 16.5

Resistance is the measure of opposition to the flow of current

The amount of current flow in a circuit (amount of energy transferred) depends on two factors:

1. 
   
   The potential difference or voltage of the power supply, such as a battery.
2. 
   
   Natural path through the load.

Formula: R = V / I

• 
  
  R is resistance in Ohms (Ω)
• 
  
  V is the potential difference (V or Volts)
• 
  
  I is the current (A or Amperes)

• longer conductors have greater resistance
• thinner wires have greater resistance than thicker wires
• larger cross-sectional area means less resistance
• "resistance of 1Ω when 1A of current flows with a potential difference of 1V across a resistor"

Resistivity is the resistance of a substance (Units: Ω x m).

Gauge number of a wire indicates its cross-sectional area.

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Resistance in Series and Parallel Circuits

Section 16.6

Kirchhoff's current law states that "the total amount of current into a junction point of a circuit equals the total current that flows out of that same junction."


Kirchhoff's voltage law states that "the total of all electrical potential decreases in any complete circuit loop is equal to any potential increases in that circuit loop."

• Kirchhoff's Voltage Law: V_T = V₁ + V₂+ V₃  
• Kirchhoff's Current Law:  I_T = I₁ = I₂ = I₃