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.