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 1 st person demonstrated the machine and asked the questions 2 nd 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: Demographics Gender distribution: Male: 40 Female: 37 Age distribution: # of Groups: 26 Groupings: Majority were families 3 scientists 1 school group of six boys

Results Question 1 What do you see happening when the crank is turned? Answers include: Electricity 13 Spark 11 Lightning 05 (mostly children) Static Electricity 04 Mentioned once: optical effect, cracking, fire, positive and negative attracting

Results Question 2 How 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 3 What 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 4 What 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 7 Does 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 8 Rank these in order of most importance/interest to you: A) Why the machine was built/what it was used for B) How it generates electricity C) How is it like lightning Almost everyone ranked (B) as their 1 st or 2 nd choice Almost everyone ranked (C) as their 2 nd or 3 rd choice (A) was split between 1 st and 3 rd 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 lightning Suggestion: 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