Based on feedback from user testing (see: PhET Faraday's Law - Gatech Interviews Notes), a number of issues were observed. This "Grab and Release" interaction sketch aims to address a number of these issues.
| Observed Issue | Example / Remark | Grab and Release Solution |
|---|---|---|
Too many alerts | Every cursor key press and release would fire location text alerts | Location text alert now fired only on release of magnet. Sonification will now be mostly uninterrupted. |
| Hard to concentrate on sounds and screen reader | Users often focus on the text alerts and miss the relationship between the magnet movement and the induced charge. | Sonification will now be mostly uninterrupted. Most text alerts have been removed from movement interaction loop, with the exception of a coil bump and play area edge bump alerts. |
| Text alerts can be out of sync with the sonification | Often when a sound event happens, like a coil bump or induced charge, text alerts report the magnets location which can create confusion or incorrect associations. | Sonification will no longer compete with most text alerts, thus avoid any confusion. Coil bumps now have a "Bumped coil" text alert. |
| Long alerts create cognitive load | A text alert can be very long (regardless of number of coils). | Alerts in general are now shorter and less complicated:
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| Long pauses in alerts causes users to stop listening | Screen readers will pause longer between sentences. | Text alerts use less periods (more commas or concatenated phrase fragments). |
| Coil bump sound can sometimes be ambiguous | Some users incorrectly associated the bump coil sound with a goal accomplishment (i.e. paraphrasing "I got the magnet into the coil, and that sound means I made it."). | A single text alert now fires when a coil bump occurs ("Bumped coil"). |
| Slide key instructions are often missed | Most users did not use the slide keys. | Introduce slide key instructions on later magnet grabs (as to not compete with other instructions, and reduce cognitive load). |
| Not clear to some users how to begin moving the magnet | The magnet button cue wasn't strong, and located in an unintuitive spot in the PDOM. |
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Issues not yet addressed:
| Observed Issue | Example / Remark | Notes |
|---|---|---|
| Unclear what sliding does | When sliding occurs, the sim can be rather silent. |
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| Unclear what voltmeter does | A number of users did know what the voltmeter was for. |
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| Unclear about use of field lines | Turning on field lines has no immediate perceivable effect. |
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Faraday's Law is an interactive sim. It changes as you play with it.
At the centre of the play area (is a coil / are two coils) connected to a light bulb circuit. There is a also moveable bar magnet.
Grab the magnet to play.
Additional controls that change what is connected to the circuit, flip the bar magnet, and reset the sim. If needed, check out keyboard shortcuts under Sim Resources.
In the circuit are a:
The coil is sideways, with openings on the left and right.
The bar magnet is left of 2 loop coil, far from 4 loop coil below.
(First sentence in this description is the same as Magnet Release Text Alerts (see below), except the word "Released" is replaced with "The bar magnet is".)
North pole on left. South pole on right.
(Polarity according to whether or not it's flipped).
| One coil | Two coils different field strengths | Two coils same field strengths | Field strength values |
|---|---|---|---|
| (field strength) magnetic field at the 4 loop coil. | (field strength) magnetic field at the 2 loop coil, (field strength) magnetic field at the 4 loop coil. | (field strength) magnetic field at both 2 loop and 4 loop coil. | Strong Moderate Weak |
| Event | Alert text |
|---|---|
| Grab magnet: 1st and 2nd time | "Grabbed, W A S D keys move in 4 directions. Press Space to release." |
| Grab magnet: 3rd - 5th time | "Grabbed, try 1 2 3 keys to slide different speeds left and right. Press Shift to stop slide. Press Space to release." |
| Grab magnet: 6th time | "Grabbed, also see keyboard shortcuts under Sim Resources. Press Space to release." |
| Grab magnet: 7th time | "Grabbed. Press Space to release." |
| Release magnet | "(Magnet Release Text Alert)" See below. |
| Bump Coil | "Bumped coil" |
| Bump Edge | "At edge of play area." |
| Bulb brightness event | "Bulb dim" "Bulb Bright" "Bulb Very Bright" "Dim / bright / very bright" |
The following diagram depicts the different text alerts fired when the magnet is released.
Unlike previous designs (and implementations), the alert strings are static and depends only on the location of the magnet in the play area when released.
The key implementation detail is being able to determine the center of the 4 loop coil, and boundaries of the two coils so the different regions can be defined.
First and Second time grabbing magnet (WASD prompt on grab)
Third to Fifth time grabbing magnet (Slide prompt on grab)
Sixth time grabbing magnet (Keyboard help prompt on grab)
Seventh time on-wards (Shortened grab alert)