The Wimshurst Machine

Evaluation Process and Results

Melanie Hopkins and Thomaie Hilaris

Content

• MSI evaluation goals

• Brief presentation/explanation of Wimshurst Machine

• Sample Questionnaire

• Evaluation process: interviews

• Results

• Conclusions

MSI evaluation goals

• Try to describe what MSI gave us as their evaluation goals. Make it short.

• Summary: Visitors separate charge using historic Wimshurst static electricity machines that produces high voltage current by electrostatic induction.

• Evaluation questions: Can people understand how it works? What contextual information (graphics or text) are most effective in promoting conceptual understanding?

The Wimshurst Machine

• Electrostatic generator

• Static electricity: Friction vs. induction

• Comparison to lightning—”homemade lightning”

Evaluation Process: Interviews

• 2 member evaluation team

• Together we introduced the project

• 1st person demonstrated the machine and asked the questions

• 2nd person took notes• After 1st 5 interviews, we

redid the labels and returned the following week to finish up with 21 more groups

Final Sample Questionnaire• What do you see happening when the crank is turned?• How would you explain this exhibit to someone who has not seen it?• What parts of the machine are easy to understand?• What parts of the machine are difficult to understand?

SHOW LABELS HERE

• Is it clear that there is a difference between the two balls (terminals)?• Is it clear how the positive and negative charges move through the machine?• Does the comparison with lightning improve the clarity or interest of the exhibit?

How?• Rank these in order of most importance or interest to you:

________Why the machine was built/what it is used for

________How it generates electricity

________How it is like lightning

Final Presentation: without labels with labels

Age distribution

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0-10 11-15 16-20 21-30 31-40 41-50 50+

Age range

Number interviewed

Results: Demographics

Gender distribution:Male: 40 Female: 37

Groupings: Majority were families3 scientists1 school group of six

boys

Results Question 1

Mentioned once: optical effect, cracking, fire, positive and negative attracting

WHAT DO YOU SEE HAPPENINING WHEN THE CRANK IS TURNED?

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Electricity Spark Lightning Static Electricity Other

Answers

Number

Results Question 2How would you explain this exhibit to someone who has not seen

it?

Answers Include:-the disks were turning (18)-the crank turned the disks (09)-the disks were turning in different directions (04)-a build up electric charge (04)-when the charge built up enough then the spark jumped

across the terminals (02)-the faster the crank was turned, the faster the machine

sparks (04)-a magnetic field (03)-used the word friction (04)-said “I don’t know” (05)

Results Question 3What parts of the machine are easy to understand?

Answers Include:

Rotating disks (10)

Turn the crank/wheel (06)

Balls (05)

It’s creating electricity (05)

Mentioned once: the metal parts, gears, rods, labels, moving too fast to see, it was mechanical

Results Question 4What parts of the machine are difficult to understand?

Answers include: Leyden jars (15)How the electricity is created or transferred

(08)The charge collectors (03)The metal sectors (03)Mentioned once: labels, noise, the balls,

why the spark is jumping, nothing was hard to understand

Results Questions 5 and 6 (with labels and comparison to lightning)

5)Is it clear that there is a difference between the two balls?6)Is it more clear how the positive and negative charges move

through the machine?

Approximately 80% answered yes to both questions

-Of these, 6 groups explained that there was a difference in charge between the two balls.

-4 groups noticed that the height of the balls was different.

Results Question 7Does the comparison with lightning improve the clarity or interest

of the exhibit? How?

Every group but one said yes.Answers for how:1)Because they look the same (05)2)Because it explains lightning (04)3)Because it’s related to the real world (02)4)Because it’s good for kids (02)5)Because it explains why the machine is on display (01)6)Because it’s important (01)7)Because you can control what you want to see (the

phenomenon?) (01)8)The comparison was interesting but did not clarify the

machine (02)

Results Question 8Rank these in order of most importance or interest to you:A) Why the machine was built/what it was used forB) How it generates electricityC) How is it like lightning

• Almost everyone ranked (B) as their 1st or 2nd choice

• Almost everyone ranked (C) as their 2nd or 3rd choice

• (A) was split between 1st and 3rd choice (this information was not on the labels)

Conclusions and Suggestions

• It is clear that the machine is generating electricity but not how

Suggestion: the machine itself requires textual and graphic support

• Mechanical parts of the machine were most intuitively clear for people but the non-moving parts of the machine (the rods and jars) were not clearSuggestion: the individual parts and functions need to be labeled on or near the machine

Conclusions and Suggestions…

• There was a more positive response to a graphic explanation rather than a textual oneSuggestion: color coding the machine, concise text support

• Overall positive response to the comparison with lightningSuggestion: Clearly parallel the two explanations

Conclusions and Suggestions

• Machine interesting for its own sake; phenomenon of lightning supportive both in terms in clarity and interest

• Ranking also suggests that history of the machine is interesting

Evaluation Preparation

• Background research on the Wimshurst machine, Book: Homemade Lightning

• Online material: mostly how to make a homemade Wimshurst Machine

• Very little material on why the machine was created or what it was used for

• Interview questions were 2 part: (1) based on observations and (2) label content interaction (what information was useful?)