Xerographic Copiers Xerographic Copiers for a doorknob, the pin - PDF document

Xerographic Copiers 1 Xerographic Copiers 2 Introductory Question Introductory Question You are covered with static electricity. If you You are covered with static electricity. If you � hold a sharp pin in your hand as you reach out hold a sharp pin in your hand as you reach out Xerographic Copiers Xerographic Copiers for a doorknob, the pin will for a doorknob, the pin will make the shock you’ll get worse make the shock you’ll get worse A. A. make the shock you’ll get weaker make the shock you’ll get weaker B. B. leave the shock you’ll get unchanged leave the shock you’ll get unchanged C. C. Xerographic Copiers 3 Xerographic Copiers 4 3 Questions about 3 Questions about Observations About Copiers Observations About Copiers Xerographic Copiers Xerographic Copiers � Copies consist of colored powder stuck to paper Copies consist of colored powder stuck to paper � How can light arrange colored powder on paper? How can light arrange colored powder on paper? � � After jams, the powder sometimes wipes off After jams, the powder sometimes wipes off � How does a copier spray charge onto a surface? How does a copier spray charge onto a surface? � � Copiers run out of colored powder or “toner” Copiers run out of colored powder or “toner” � How does a copier make its copies permanent? How does a copier make its copies permanent? � � Copies are often warm after being made Copies are often warm after being made � Copies tend to be Copies tend to be staticy staticy and clingy and clingy � Some copiers scan a light, some use a flash Some copiers scan a light, some use a flash Xerographic Copiers 5 Xerographic Copiers 6 Question 1 Question 1 The Xerographic Concept The Xerographic Concept � The xerographic concept The xerographic concept � How can light arrange colored powder on paper? How can light arrange colored powder on paper? � � sprays electric charge onto a surface and sprays electric charge onto a surface and � projects an image of the document onto that surface. projects an image of the document onto that surface. � Wherever light hits the surface, the charge escapes. Wherever light hits the surface, the charge escapes. g g , , g g p p � The remaining charge attracts colored toner particles The remaining charge attracts colored toner particles � which are then bonded to paper to produce a copy. which are then bonded to paper to produce a copy. � The surface is a photoconductor, The surface is a photoconductor, � an insulator that turns into a conductor in the light, an insulator that turns into a conductor in the light, � so illumination allows charge to move and escape. so illumination allows charge to move and escape. 1

Xerographic Copiers 7 Xerographic Copiers 8 Question 2 Question 2 Electric Fields Electric Fields (Part 1) (Part 1) � How does a copier spray charge onto a surface? How does a copier spray charge onto a surface? � Consider these two views of electric forces: Consider these two views of electric forces: � The first view is The first view is charge charge- -on on- -charge charge � Charge Charge 1 pushes directly on Charge pushes directly on Charge 2 2 . . � The second view is The second view is charge charge- -electric field electric field- -charge charge � Charge Charge 1 creates an electric field creates an electric field � That electric field pushes on Charge That electric field pushes on Charge 2 2 . . � This electric field isn’t a fiction; it actually exists! This electric field isn’t a fiction; it actually exists! Xerographic Copiers 9 Xerographic Copiers 10 Electric Fields Electric Fields (Part 2) Clicker Question Clicker Question (Part 2) � An electric field An electric field � To determine the electric field at the tip of your To determine the electric field at the tip of your � nose, you could throw a + test charge past your nose, you could throw a + test charge past your � is a structure in space that pushes on electric charge is a structure in space that pushes on electric charge nose and, ignoring gravity, measure nose and, ignoring gravity, measure � is vector in character: it has magnitude and direction is vector in character: it has magnitude and direction � m � may depend on position and time may depend on position and time m d p nd n p d p nd n p iti n nd tim iti n nd tim � The electric field at a given position and time The electric field at a given position and time A. its velocity at the tip of your nose. its velocity at the tip of your nose. � A. � is proportional to the force on a + test charge is proportional to the force on a + test charge B. its position at the tip of your nose. its position at the tip of your nose. B. � is often represented graphically by an arrow is often represented graphically by an arrow C. its acceleration at the tip of your nose. its acceleration at the tip of your nose. C. � but is actually located at just one point on that arrow but is actually located at just one point on that arrow D. its mass at the tip of your nose its mass at the tip of your nose D. Xerographic Copiers 11 Xerographic Copiers 12 Electric Fields and… Electric Fields and… …Voltage Gradients …Voltage Gradients � Consider these two views of electric forces: Consider these two views of electric forces: � The second view is The second view is voltage gradient voltage gradient- -on on- -charge charge � The first view is The first view is electric field electric field- -on on- -charge charge � An object accelerates to reduce potential energy (PE) An object accelerates to reduce potential energy (PE) � so it experiences a force down the “gradient” of PE so it experiences a force down the “gradient” of PE � An electric field exerts a force on a + test charge An electric field exerts a force on a + test charge � + test charge has electrostatic potential energy (EPE) � + t t h r + test charge has electrostatic potential energy (EPE) + t t h r h h l l tr tr t ti p t nti l n r t ti p t nti l n r (EPE) (EPE) � + test charge’s EPE is proportional to its voltage + test charge’s EPE is proportional to its voltage � + test charge experiences force down voltage gradient + test charge experiences force down voltage gradient � A voltage gradient exerts a force on a + test charge A voltage gradient exerts a force on a + test charge � A voltage gradient A voltage gradient is is an electric field! an electric field! 2