Resistance

What is Resistance?

  • Resistance is a property of electrical circuits that opposes the flow of current.
  • Resistance is measured in ohms (Ω).

Factors Influencing Resistance

  • Length of conductor: Longer conductors have higher resistance.
  • Thickness of conductor: Thinner conductors have higher resistance.
  • Material of conductor: Different materials have different resistivity.
  • Temperature: As temperature increases, resistance increases (except in semiconductors).

Ohm’s Law

  • Ohm’s Law states that the current through a conductor between two points is directly proportional to the voltage across the two points.
  • Mathematically expressed as: I = V/R, where I is the current, V is the voltage, and R is the resistance.

Resistors

  • Fixed resistors have a resistance that does not change.
  • Variable resistors can change their resistance.
  • Resistors in series add to give the total resistance: R_total = R1 + R2 + …
  • Conversely, resistors in parallel follow the formula: 1/R_total = 1/R1 + 1/R2 + …

Superconductors

  • Superconductors are materials that have zero resistance at very low temperatures.
  • Superconductors can cause a current to flow indefinitely without the need for a continuous supply of energy.

Resistance and Power

  • The power (P) of an electrical circuit with resistance can be calculated using the equation: P = I^2R where I is the current and R is the resistance.
  • Alternatively, the power can also be calculated using the equation: P = VI, where V is the voltage.

Potential Differences and Components

  • There are potential differences across different components due to the resistance. For instance, the potential difference across a resistor in a circuit is given by Ohm’s Law: V = IR.
  • The potential difference (V) across a component in a series circuit is shared, but in a parallel circuit, it is the same across all components.