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Why a Theater Sensor Signals When Wet 4 questions
Why a Theater Sensor Signals When Wet
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A theater class models a water sensor with two contacts separated by a small gap. The sensor signals when charge moves through material spanning the gap. A copper strip gives a signal. A clean gap gives no signal when dry or when covered with deionized water.
Question 1
The copper strip produces a signal without dissolving. Explain what moves charge through solid copper.
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Two new marks each span the gap. One mark is a graphite trace that remains attached when rinsed. The other is a deposit of potassium chloride that can be rinsed away with deionized water. The class measures each mark when dry, when wet with deionized water, and again after rinsing and drying.
| Mark | Dry | Wet | After rinsing and drying |
|---|---|---|---|
| X | Signal | Signal | Signal |
| Y | No signal | Signal | No signal |
Question 2
Which identification fits the complete set of observations?
- X is potassium chloride and Y is graphite.
- Both marks are graphite.
- X is graphite and Y is potassium chloride.
- The observations cannot distinguish the two marks.
Question 3
Both wet marks produce the same signal. Explain how the two wet marks can carry charge using different kinds of particles.
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Question 4
After rinsing and drying, mark Y gives no signal. A student concludes that the test proves all the potassium chloride was removed. Explain why a dry reading alone cannot establish this.
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