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Resistance & Water Model

Resistance & Water Model. Text11.1: 441-445. Agenda. Review Resistance What is it? Resistors Water Model Lab Consolidation. Learning Goal. By the end of this class, we should be able to: Define and identify the correct units and measurement tool of resistance

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Resistance & Water Model

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  1. Resistance & Water Model Text11.1: 441-445

  2. Agenda • Review • Resistance • What is it? • Resistors • Water Model • Lab Consolidation

  3. Learning Goal • By the end of this class, we should be able to: • Define and identify the correct units and measurement tool of resistance • Describe resistance and current in terms of the water model

  4. Minds On • How do we control the flow of electricity?

  5. Minds On • How does power get to your house?

  6. Minds On • How can we use that power in our house?

  7. Minds On • How can my electronics use/control the electricity?

  8. Resistance • Is the degree to which a substance opposes the flow of electric current through it • All substances allow electron flow to through them to some extent • So nothing is entirely resistant to current

  9. Resistance • Conductors, such as metals, allow electrons to flow through it fairly easily and therefore have limited resistance • Insulators are vice-versa • More resistance the lower the conductivity

  10. Resistance • Resistance is measured with an ohmmeter • Units are in ohms (Ω) • Multimeterscan also be used which have a combination of all 3 meters (potential difference, current or resistance)

  11. Resistance • Resistance results in the slowing of electrons and transfers the electrical energy into other forms of energy • Like heat and/or light • i.e. heaters are resistors for a purpose, filaments in a light bulb are resistors

  12. Other Factors Effecting Resistance

  13. Resistors: Type 1 • Wire wound: • Has a wire mask of heat-resistant metal wrapped in an insulating core • The longer/ thinner the wire the more the resistance • Usually 0.1 Ω -200k Ω • 200k Ω = thinnest

  14. Resistors: Type 2 • Carbon-composition: • Made of carbon mixed with other materials • Carbon mixture is moulded into a cylinder with a wire at each end • By varying the size and composition of the cylinder the resistances can vary from 10 Ω to 20 M200k Ω • Cheaper but less precise

  15. Resistors • Resistors can be used to control current (or the potential difference) in a circuit • Always remember that they can create heat and can burn so you should be cautious when using them

  16. Water Model • Think of these new concepts in terms of pipes filled with water • Not all pipes transport water equally well. The longer and thinner the pipe is, the more resistant it is to water flowing through it • The easiest way for water to flow through is a wide short tube

  17. Water Model • Think of the circuit as a pipe • Amount of water following through a specific portion on the tube per second is like current • Resistance is the size of the tube

  18. Lets Test Some More! • Mini-Lab – The Effect of Resistance on an Electric Circuit

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