---
title: Resistivity Variations
topic: Circuits
author: John Hopkinson
source: Physics 122 2019 Final Q8
template_version: 1.4
attribution: standard
partialCredit: false
singleVariant: false
showCorrectAnswer: false
outcomes:
- 21.3.3.0
difficulty:
- easy
randomization:
- 0
taxonomy:
- undefined
span:
- chapter
length:
- short
tags:
- L.K
assets: null
part1:
  type: multiple-choice
  pl-customizations:
    weight: 1
myst:
  substitutions:
    params:
      vars:
        title: Resistivity Variations
      part1:
        ans1:
          value: The resistivity of the copper pipe increased at lower temperatures,
            resulting in decreased induced currents, and the induced magnetic fields
            opposed the magnet's falling.
          feedback: Try Again!
        ans2:
          value: The resistivity of the copper pipe decreased at lower temperatures,
            resulting in increased induced currents, and the induced magnetic fields
            opposed the magnet's falling.
          feedback: Great! You got it.
        ans3:
          value: The rate of change in the magnetic flux in the pipe caused by the
            falling magnet was greater in the colder pipe, resulting in a larger induced
            emf.
          feedback: Try Again!
        ans4:
          value: Copper became magnetic at the lower temperature, so the magnet stuck
            to its side.
          feedback: Try Again!
        ans5:
          value: Copper became superconducting at the lower temperature so it expelled
            the magnet.
          feedback: Try Again!
---
# {{ params.vars.title }}
Dropping a strong magnet through a $20 \textrm{ cm}$ copper tube took about $3 \textrm{ s}$ when the pipe was at room temperature and $4 \textrm{ s}$ when the pipe had been cooled in liquid nitrogen for a short period of time.

## Part 1

The magnet fell more slowly through the cooled pipe because:

### Answer Section

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## Attribution

Problem is licensed under the [CC-BY-NC-SA 4.0 license](https://creativecommons.org/licenses/by-nc-sa/4.0/).<br> ![The Creative Commons 4.0 license requiring attribution-BY, non-commercial-NC, and share-alike-SA license.](https://raw.githubusercontent.com/firasm/bits/master/by-nc-sa.png)