Resistance in a wire
Resistance in a wire is caused by the positive metal ions in the metal blocking the flow of electrons.
The type of material determines the resistance (but so do other things like the length and thickness of the wire).
Resistance is inversely proportional to the current (if the potential difference is constant). This means that as resistance increases, current decreases.
Resistance is directly proportional to the potential difference (if the current is constant). This means that as resistance increases, potential difference increases.
Factors affecting resistance
- Area of cross-section (thickness)
- Thicker wires have less resistance
- That’s because there is more space for the electrons to flow through without colliding with the metal ions
- Length of wire
- Longer wires have more resistance
- Temperature
- Higher temperatures increase resistance
- That’s because, at higher temperatures, the metal ions vibrate more so collide with the electrons more frequently
- Material
- Some materials have more resistance than others
- This is called the material’s resistivity
flashcards
| Question | Answer |
|---|---|
| What causes resistance in a wire? | Resistance is caused by positive metal ions in the metal blocking the flow of electrons. |
| What is the relationship between resistance and current (with constant potential difference)? | Resistance is inversely proportional to the current (as resistance increases, current decreases). |
| What is the relationship between resistance and potential difference (with constant current)? | Resistance is directly proportional to the potential difference (as resistance increases, potential difference increases). |
| How does the thickness of a wire affect its resistance? | Thicker wires have less resistance because there is more space for electrons to flow without colliding with metal ions. |
| How does the length of a wire affect its resistance? | Longer wires have more resistance. |
| How does temperature affect resistance? | Higher temperatures increase resistance because metal ions vibrate more and collide with electrons more frequently. |
| What is the property that determines how much resistance a material has? | The material’s resistivity. |