Background

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 IssueExample / RemarkGrab 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 readerUsers 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 sonificationOften 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 loadA text alert can be very long (regardless of number of coils).

Alerts in general are now shorter and less complicated:

  • Removed play area location alerts.
  • Reduced the complexity of proximity and regions.
Long pauses in alerts causes users to stop listeningScreen readers will pause longer between sentences.Text alerts use less periods (more commas or concatenated phrase fragments).
Coil bump sound can sometimes be ambiguousSome 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 missedMost 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 magnetThe magnet button cue wasn't strong, and located in an unintuitive spot in the PDOM.
  • Better label and aria-description for better cueing ("Grab Magnet" and "Select this to move the magnet").
  • Button to grab the magnet is now located in the Controls Area list with other controls.


Issues not yet addressed:

Observed IssueExample / RemarkNotes
Unclear what sliding doesWhen sliding occurs, the sim can be rather silent.
  • Is this a concern? Users may not have used it sufficiently to gain clarity
  • Are there magnet movement sounds when sliding occurs? (i.e. movement ticks).
Unclear what voltmeter doesA number of users did know what the voltmeter was for.
  • Is this a concern? Most users will use FL in context of a learning unit.
  • The voltmeter could be defined in the description instead (i.e. "Voltmeter - measures the positive / negative charge flowing through the circuit.")
  • The voltmeter is initially available - AP suggested it should be hidden by default
Unclear about use of field linesTurning on field lines has no immediate perceivable effect.
  • Currently the design only updates the "Magnetic Field Lines" description as the magnet moves.
  • Should the field strength be added to the text alert when magnet is released?


Notes:

PDOM Example

Faraday's Law (h2, Scene Summary)

ExampleTemplate*

Faraday's Law‬ is an interactive sim. It changes as you play with the movable bar magnet.

At the centre of the play area are a 2 loop and a 4 loop coil connected to a light bulb circuit.A voltmeter is also attached to the circuit.

The two coils are sideways, both with openings on the left and right.

Magnetic field is weak  at the 2 loop coil, moderate magnetic field at the 4 loop coil.

Grab the magnet to play.

There are 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.

"Faraday's Law‬ is an interactive sim. It changes as you play with the movable bar magnet."

"At the centre of the play area" + (is a 4 loop coil / are a 2 loop and a 4 loop coil) + "connected to a light bulb circuit." /If voltmeter attached/ "A voltmeter is also attached to the circuit."

"The" + (coil is / two coils are) + "sideways," + (with / both with) + "openings on the left and right."

/ If field lines visible - One coil /
"Magnetic field is" + (strong / moderate / weak) + "at the coil."

/ If field lines visible - Two coils with different field strengths /
"Magnetic field is" + (strong / moderate / weak) + "at the 2 loop coil," + (strong / moderate / weak) + "magnetic field at the 4 loop coil."

/ If field lines visible - Two coils, same field strengths /
"Magnetic field is" + (strong / moderate / weak) + "at both coils."

"Grab the magnet to play.

There are 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."

* Emphasis added for legibility

Play Area (h2)

Bar Magnet (h3)

ExampleTemplate

Magnet above right of 2 loop coil.

Magnet North pole on left South on right.

(Button "Grab magnet")

"

/ If one coil /

Follows "Magnet Release Text Alerts - One Coil" (see below), but the word "Released" replaced with "Magnet".

/ If two coils /

Follows "Magnet Release Text Alerts - Two Coils" (see below), but the word "Released" replaced with "Magnet".

/ Polarity according to whether or not it's flipped /

"Magnet" + (North / south) + "pole on left" + (South / North) + "on right."

Button: "Grab magnet"

"Once grabbed, W A S D and Arrow Keys moves magnet in 4 directions, 1 2 3 keys slides magnet left and right different speeds."

(question) Insert instructions on cursor moves and sliding. Make sure to mention that they have to grab first "once grabbed".



Controls Area (h2)

Text Alerts

EventAlert 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"

Magnet Release Text Alerts

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.

Magnet Release Text Alerts - One Coil

Region #Magnet Release Alert TextRegion #Magnet Release Alert Text
1, 4, 9

“Released above left of coil.”

15“Released just right of coil.”
2, 5, 6, 7, 10“Released, above coil.”16“Released right of coil.”
3, 8. 11

“Released above right of coil.”

17“Released below left of coil.”
12“Released left of coil.”18“Released just below coil.”
13“Released just left coil.”19“Released below right of coil.”
14“Released inside coil.”

Magnet Release Text Alerts - Two Coils

Region #Magnet Release Alert TextRegion #Magnet Release Alert Text
1“Released above left of 2 loop coil.”12"Released left of 4 loop coil."
2"Released just above 2 loop coil"13"Released just left of 4 loop coil."
3"Released above right of 2 loop coil"14"Released inside 4 loop coil."
4"Released left of 2 loop coil"15"Released just right of 4 loop coil."
5"Released just left of 2 loop coil"16"Released right of 4 loop coil."
6"Released inside 2 loop coil"17"Released below left of 4 loop coil."
7"Released just right of 2 loop coil."18"Released just below 4 loop coil."
8"Released right 2 loop coil."19"Released below right of 4 loop coil."




9"Released left of both coils."11"Released right of both coils."
10"Released between both coils."

Example Text Alert Interaction

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)