184_notes:charging_discharging

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184_notes:charging_discharging [2019/01/04 00:47] – dmcpadden184_notes:charging_discharging [2021/01/25 01:07] (current) – [Charging] bartonmo
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-[[184_notes:pc_force|Next Page: Electric Force]]+/*[[184_notes:pc_force|Next Page: Electric Force]]
  
-[[184_notes:charge_and_matter|Previous Page: Charge and Matter]]+[[184_notes:charge_and_matter|Previous Page: Charge and Matter]]*/
  
 ===== Charging and Discharging ===== ===== Charging and Discharging =====
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 Objects become charged by either gaining extra electrons (becoming negatively charged) or by giving up electrons (becoming positively charged). There are generally two ways to create charged objects: //by conduction// or //by induction//. Objects become charged by either gaining extra electrons (becoming negatively charged) or by giving up electrons (becoming positively charged). There are generally two ways to create charged objects: //by conduction// or //by induction//.
-[{{  184_notes:tape.png?200|Tape charging by conduction}}]+[{{  184_notes:tape.png?200|Tape being pulled apart, therefore charging by conduction}}]
  
   * **Charging by conduction** means charging by contact. For example if you have one piece of tape on top of another then rip them apart, electrons or negative ions from one piece of tape are transferred to the other, making one tape negatively charged and leaving the other positively charged. This happens by breaking the polymers that make up the tape adhesive. Which materials will take electrons and which materials will give up electrons is highly dependent on the chemical composition of the materials and which material it is paired with (the specific adhesive used in the tape, in this case). In a well known case, a plastic rod will gain electrons (become negatively charged) when rubbed with wool, but the same plastic rod will lose electrons (become positively charged) when rubbed with silk. When charging by conduction, rubbing is not necessary for charges to transfer - only contact is needed, but rubbing increases the time and parts of the surfaces that are in contact, which helps facilitate this transfer.   * **Charging by conduction** means charging by contact. For example if you have one piece of tape on top of another then rip them apart, electrons or negative ions from one piece of tape are transferred to the other, making one tape negatively charged and leaving the other positively charged. This happens by breaking the polymers that make up the tape adhesive. Which materials will take electrons and which materials will give up electrons is highly dependent on the chemical composition of the materials and which material it is paired with (the specific adhesive used in the tape, in this case). In a well known case, a plastic rod will gain electrons (become negatively charged) when rubbed with wool, but the same plastic rod will lose electrons (become positively charged) when rubbed with silk. When charging by conduction, rubbing is not necessary for charges to transfer - only contact is needed, but rubbing increases the time and parts of the surfaces that are in contact, which helps facilitate this transfer.
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 If you touch the tape, your finger acts as a neutral conductor and the charges are able to move from the tape into your finger. Unfortunately, you cannot shock your friend using your finger because the charges then spread through your body and you are not adding enough charge compared to all the charges and atoms in your body to be able to notice. We call a vast collection of positive and negative charges **an electrical ground** or just **ground** (it is called ground because the Earth is typically used as an electrical ground). A ground is able to absorb small amounts of charge and remain neutral because the added charge is so small compared to the total number of charges in the ground. In the tape example, your body was acting as a ground. The symbol for a ground is three horizontal lines, decreasing in size (shown to the right). If you touch the tape, your finger acts as a neutral conductor and the charges are able to move from the tape into your finger. Unfortunately, you cannot shock your friend using your finger because the charges then spread through your body and you are not adding enough charge compared to all the charges and atoms in your body to be able to notice. We call a vast collection of positive and negative charges **an electrical ground** or just **ground** (it is called ground because the Earth is typically used as an electrical ground). A ground is able to absorb small amounts of charge and remain neutral because the added charge is so small compared to the total number of charges in the ground. In the tape example, your body was acting as a ground. The symbol for a ground is three horizontal lines, decreasing in size (shown to the right).
  
-From the calculation side, dealing with discharging objects is dependent on time and is very complicated. For the purpose of this class, //__we will often make the assumption that discharging does not occur__//. Another way to say this would be that we assume //__charge is constant__//, or we assume that the charged object does not interact with the air or another surface. +From the calculation side, dealing with discharging objects is dependent on time and is very complicated. For the purpose of this class, //__we will often make the assumption that discharging does not occur__//. Another way to say this would be that we  //__ assume charge is constant__//, or we __//assume that the charged object does not interact with the air or another surface. 
 +// 
 +__
 ==== Examples ==== ==== Examples ====
 [[184_notes:examples:Week2_conducting_insulating_balls|Attempting to Charge Insulators by Induction]] [[184_notes:examples:Week2_conducting_insulating_balls|Attempting to Charge Insulators by Induction]]
  
 [[https://www.youtube.com/watch?v=cMM6hZiWnig|Demonstration of charging by induction]] [[https://www.youtube.com/watch?v=cMM6hZiWnig|Demonstration of charging by induction]]
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