State what is meant by superconductivity.
Explain the required conditions for the material to become superconducting. (3 marks)
- Superconductivity means a material has zero resistivity/resistance
- Resistivity decreases with temperature or idea of cooling
- Becomes superconducting when you reach the critical temperature
State and explain what happens to the resistance of the cable when the embedded
filaments of wire are made superconducting (3 marks)
- The resistance decreases (to zero)
- Copper still has resistance
- But this is in parallel with filaments (which have zero resistance)
- Therefore total resistance=0
What instrument would you use to make measurements of regular objects?
Vernier Calipers
Elastic Limit:
Where a material no longer shows elastic behaviour, and hookes law no longer applies.
Why does a material no longer show elastic behaviour after a certain amount of force has been applied?
Some of the atomic bonds become fractured due to excessive force
Units of spring constant (k):
Nm-1
Two springs of spring constant k are connected in parallel (side by side) and a weight hangs down from them. What is the combined spring constant?
k+k = 2k
Two springs of spring constant k are connected in series (one hangs down from the other), What is the combined spring constant?
1/Kt = 1/K1 + 1/K2
Two springs are hung in series (one attached to the other). If one of the strings has a greater k (more stiff), or a greater diameter, does one spring have more tension than the other?
Tension in each spring is the SAME for each regardless if one spring is stronger.
UTS:
Ultimate tensile stress
Highest stress that can be applied to an object before it breaks (Highest point on graph)
Plastic flow:
Where no extra force is applied but the strain continues to increase (can be observed on a reasonably horizontal point on a graph)
Think blu tac extending and still moving after you stop pulling/stretching it
Strain energy
Energy required to permanently deform a material
