Wimshurst Machine

Evaluation Process and Results

Melanie Hopkins and Thomaie Hilaris

MSCOPE and MSI 2007

MSI Evaluation Goals

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

• Potential Interactive Opportunities: operate Wimshurst machine artifact to generate static electricity and discharge of sparks

• Evaluation questions: Can people understand how it works [that it is separating charges]? 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

• 1st person demonstrated the machine and asked the questions

• 2nd person took notes

• Revision of labels

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

Results: DemographicsGender distribution:

Male: 40 Female: 37

Age distribution:

02468

101214161820

0-10

11-1

5

16-2

0

21-3

0

31-4

0

41-5

0

50+

# of Groups: 26

Groupings: Majority were families3 scientists1 school group of six boys

Results Question 1What do you see happening when the crank is

turned?

Answers include: Electricity 13 Spark 11Lightning 05 (mostly children)Static Electricity 04

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

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)-friction (04)

-“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

Approximately 80% answered yes to both questions

-6 groups: difference in charge between the two balls.

-4 groups: noticed height of the balls is different.

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

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 it’s on display (01)6)Because it’s important (01)7)Interesting but did not clarify the machine (02)8)Because you can control what you want to see [the phenomenon?]

(01)

improved concept

improved interest

Results Question 8Rank these in order of most importance/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 (not mentioned

the labels)

Conclusions

• Clear that the machine is generating electricity but not how

Suggestion: the machine itself requires textual/graphic support

• Mechanical parts of the machine are intuitively clear but non-moving parts of the machine (the rods and jars) are not

Suggestion: individual parts and functions need to be labeled on/near the machine

Can people understand how it works [that it is separating charges]?

• More positive response to a graphic explanation rather than a textual one

Suggestion: color coding the machine, concise text support

What contextual information (graphics or text) are most effective in promoting conceptual understanding?

++

+

++

+

+

+

+ + +

--

--

--

----

---

-

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

+ +

-

+ + + + +

------- -

NEGATIVELY CHARGED CLOUDS

POSITIVELY CHARGED GROUND

-

Finally:

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

Ranking (Question 8) suggests that history of the machine is also interesting

Content

• MSI evaluation goals

• Brief presentation/explanation of Wimshurst Machine

• Sample Questionnaire

• Evaluation process: interviews

• Results

• Conclusions