You are Here: Home >< Physics

# Resistance/Super Conductivity question watch

Announcements
1. The diagram below shows the cross–section of a cable consisting of parallel filaments that
can be made superconducting, embedded in a cylinder of copper
State and explain what happens to the resistance of the cable when the embedded filaments of wire are made superconducting.

One of the solutions is: Copper still has resistance but it is in parallel with filaments with zero resistance so total resistance is zero...
This didn't make sense to me.. I thought superconductivity meant there was no resistance in the actual material so why does copper still have resistance. and also if its in parallel then why does that mean that its overal resistance is zero :/
thanks
The diagram below shows the cross–section of a cable consisting of parallel filaments thatcan be made superconducting, embedded in a cylinder of copperState and explain what happens to the resistance of the cable when the embedded filaments of wire are made superconducting.One of the solutions is: Copper still has resistance but it is in parallel with filaments with zero resistance so total resistance is zero...This didn't make sense to me.. I thought superconductivity meant there was no resistance in the actual material so why does copper still have resistance. and also if its in parallel then why does that mean that its overal resistance is zero :/thanks
How do we calculate total resistance in a parallel circuit?
3. (Original post by an_atheist)
How do we calculate total resistance in a parallel circuit?
1/R1 + 1/R2 + 1/R3 etc.. which would make the resistance zero.. but apparently the copper still has resistance :/
4. Superconducting materials in their superconductor states have 0 resistance whether in parallel or in series. In this scenario the copper and the superconductor are connected in parallel so the current has two options, going down the zero resistance path or going down the resistance path (copper) or both. In total the resistance is the resistance of the copper but the circuit behaves as though it has no resistance because the current flows through the superconductor not the copper. In this scenario the copper has essentially been cut out of the circuit.

The key thing here is that the copper isn't superconducting, so it's the higher resistance route.
5. (Original post by Peroxidation)
Superconducting materials in their superconductor states have 0 resistance whether in parallel or in series. In this scenario the copper and the superconductor are connected in parallel so the current has two options, going down the zero resistance path or going down the resistance path (copper) or both. In total the resistance is the resistance of the copper but the circuit behaves as though it has no resistance because the current flows through the superconductor not the copper. In this scenario the copper has essentially been cut out of the circuit.

The key thing here is that the copper isn't superconducting, so it's the higher resistance route.
Ah, that's brilliant.. thanks!
6. It takes the path of least resistance. Literally

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: April 4, 2016
Today on TSR

10 instant mood-lifters

### University open days

• University of the Arts London
MA Performance Design and Practice Open Day Postgraduate
Thu, 24 Jan '19
• Brunel University London
Sat, 26 Jan '19
• SOAS University of London