Chose the correct answer: 1. You electrically charge a plastic rod by rubbing it against fur. You then place the rod near a few little pieces of paper and the pieces of paper stick to the plastic rod. Explain why this happens. Think of what happens to the charge inside of the pieces of paper. The charged rod transfers electrons to the pieces of paper, creating charge unbalance. The excess negative charge on the plastic rod attracts the negative charges in the pieces of paper, causing charge polarization. The charged fur transfers electrons to the pieces of paper, creating charge unbalance. The charged paper transfers electrons to the rod, creating charge unbalance. The charged rod transfers protons to the pieces of paper, creating charge polarization. The paper is a naturally charged object so it is attracted by the plastic rod. It is impossible to determine because we don't know the amount of charge on each. 2. When you rub a glass rod with silk you electrically charge the glass rod (and the silk). Likewise, when you rub a plastic rod with fur you electrically charge the plastic rod (and the fur). However, when you place the charged rods near each other you notice that they attract. What can you conclude about the sign of the charge on each? Can you determine just from this experiment the sign of the charge on each rod? Yes, they have equal charges, either positive or negative. Yes, the have opposite charges, the glass rod is negative and the plastic rod is positive. Yes, the have opposite charges, the plastic rod is negative and the glass rod is positive. If the two rods attract each other, then we can conclude that they have opposite charges. However, we cannot conclude from this experiment alone which one is negative and which one is positive. SInce the two rods attract each other they must have like charges, because like charges attract. However, we cannot determine the sign. No conclusion can be made without knowing the magnitude of the charges. The sign of the charge can be determined calculating the acceleration. 3. The brightness of a lightbulb is dependent on the current that goes through the lightbulb (in reality on the power, which is I^2/R). In Europe, the voltage used is 220 Volts, as opposed to the 120 Volts used in the USA. Will a lighbulb that is made for European voltage work well or poorly in the USA? It will work poorly in the USA. Since I=V/R, if V decreases, so does I, and so does the brightness. It will work more efficiently in the USA. Since I=V/R, if V decreases, I increases, and the brightness increases. It will work better in the USA because the resistance of the wires is smaller. Whether it works better or worse depends on how modern the wiring system is, regardless of the voltage, V.
Chose the correct answer:
1. You electrically charge a plastic rod by rubbing it against fur. You then place the rod near a few little pieces of paper and the pieces of paper stick to the plastic rod. Explain why this happens. Think of what happens to the charge inside of the pieces of paper.
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The charged rod transfers electrons to the pieces of paper, creating charge unbalance. |
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The excess negative charge on the plastic rod attracts the negative charges in the pieces of paper, causing charge polarization. |
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The charged fur transfers electrons to the pieces of paper, creating charge unbalance. |
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The charged paper transfers electrons to the rod, creating charge unbalance. |
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The charged rod transfers protons to the pieces of paper, creating charge polarization. |
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The paper is a naturally charged object so it is attracted by the plastic rod. |
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It is impossible to determine because we don't know the amount of charge on each. |
2. When you rub a glass rod with silk you electrically charge the glass rod (and the silk). Likewise, when you rub a plastic rod with fur you electrically charge the plastic rod (and the fur). However, when you place the charged rods near each other you notice that they attract. What can you conclude about the sign of the charge on each? Can you determine just from this experiment the sign of the charge on each rod?
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Yes, they have equal charges, either positive or negative. |
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Yes, the have opposite charges, the glass rod is negative and the plastic rod is positive. |
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Yes, the have opposite charges, the plastic rod is negative and the glass rod is positive. |
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If the two rods attract each other, then we can conclude that they have opposite charges. However, we cannot conclude from this experiment alone which one is negative and which one is positive. |
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SInce the two rods attract each other they must have like charges, because like charges attract. However, we cannot determine the sign. |
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No conclusion can be made without knowing the magnitude of the charges. |
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The sign of the charge can be determined calculating the acceleration. |
3. The brightness of a lightbulb is dependent on the current that goes through the lightbulb (in reality on the power, which is I^2/R). In Europe, the voltage used is 220 Volts, as opposed to the 120 Volts used in the USA. Will a lighbulb that is made for European voltage work well or poorly in the USA?
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It will work poorly in the USA. Since I=V/R, if V decreases, so does I, and so does the brightness. |
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It will work more efficiently in the USA. Since I=V/R, if V decreases, I increases, and the brightness increases. |
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It will work better in the USA because the resistance of the wires is smaller. |
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Whether it works better or worse depends on how modern the wiring system is, regardless of the voltage, V. |
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