these question are desined to focus and refine your reasoning skills. a- It is s
ID: 582828 • Letter: T
Question
these question are desined to focus and refine your reasoning skills.
a- It is said that like charges repel. You should have observed that after the two pieces of scotch tape are pulled quickly off a table the tapes repel each other. Perhaps each tape has a different type of charge and the rule has been stated backwards. Why do you believe that the charges on the two tapes are like types of charges? Note: It is not acceptable to answer “because like charges repel and I observed the repulsion.”
b- It is said that like charges repel. You should have observed that after two lightweight metal covered balls are stroked with a plastic rod that has been rubbed with fur the balls repel each other. Perhaps each ball has an opposite charge and the rule has been stated backwards. Why do you believe that the charges on the two balls are the same? Note: It is not acceptable to answer “because like charges repel and I observed the repulsion.”
c- It is said that unlike charges attract. You should have observed that after the sticky side of a piece of scotch tape is pulled quickly off the smooth side of another piece of tape the tapes attract each other. Perhaps each tape has the same type of charge and the rule has been stated backwards. Why do you believe that the charges on the two tapes are different? Note: It is not acceptable to answer “because unlike charges attract and I observed the attraction.”
d- It is said that unlike charges attract. You should have observed that when one light weight metal covered ball is stroked with a plastic rod that has been rubbed with fur and the other ball is stroked with a glass rod that has been rubbed with polyester, then the the two balls attract each other. Perhaps each ball has a like charge and the rule has been stated backwards. Why do you believe that the charges on the two balls are different? Note: It is not acceptable to answer “because unlike charges attract and I observed the attraction.”
d- Consider four lightweight metal coated balls suspended on nonconducting threads as shown in the diagram that follows.
Suppose ball A is stroked with a plastic rod that has been rubbed with fur. When you observe interactions between pairs of balls one at a time you find that:
1. B, C, and D are each attracted to A.
2. B and C seem to have no effect on each other.
3. B and C are both attracted to D.
What is the net charge on each of the balls? Which ones, if any, have positive charge? Negative charge? No charge at all? Explain your reasoning.
Explanation / Answer
(a) Scotch tape likes to gain electrons from other materials and become negative. When you pull both pieces of tape up from the desk, they are ripping away some of the electrons in the desk, leaving both strips of tape negatively charged. Negatively charged ions in any material are unstable and seek stability by looking for positive charges so that they can donate their electrons to the positive charges. Since both the tapes are negatively charged, they don't show any affinity for each other and tend to go away from each other. Thus they repel.
(b) Metal balls likes to lose electrons to other materials and become positive. Positively charged ions in any material are unstable and seek stability by looking for negative charges so that they can gain their electrons and become neutral or stable. Since both the balls are positively charged, they don't show any affinity for each other and tend to go away from each other. Thus they repel.
(c) One of the pieces of tape takes some of the charge from the other piece, leaving them with overall opposite charges. The positively charged ions seek for electrons to become neutral or stable and negatively charged ions seek to lose electrons to become stable. Thus they attract each other.
(d) When one light weight metal covered ball is stroked with a plastic rod that has been rubbed with fur, the metal ball acquires positive charge. Also, when another ball is stroked with a glass rod that has been rubbed with polyester, the metal ball acquires negative charge. The positively charged ions seek for electrons to become neutral or stable and negatively charged ions seek to lose electrons to become stable. Thus they attract each other.
(e) (1) Since ball A is rubbed to plastic rod, it acquires positive charge. If B, C, and D are each attracted to A, then it implies that B,C and D have opposite charge to what A has. That is B, C and Dcan be negatively charged or neutral.
(2) If B and C seem to have no effect on each other, it implies that they don't have any charge on them. That is B and C are neutral.
(3) If B and C are both attracted to D, that means B and C can have opposite charge to D or they can also neutral.
So, from above discussion, we can conclude that A is positively charged, B and C are neutral and D is negatively charged.
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