lecture 02 – ppt and i-clicker questions which picture best represents the movement of changes as...
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Lecture 02 – PPT and I-Clicker Questions
Which picture best represents the movement of changes as a negatively charged object comes near a neutral sphere?
(A) (B)
(C) (D)
(E)
Charging objects by induction
“Ground” – an infinite source or sink of charge
Note asymmetric charge distribution in sphere. Why?
Note more + charges than negative. Why?
Charges have rearranged again. Why?
Balloon “sticking” to wall.
I-Clicker Question
Which of the following insights concerning the electric field at a distance D from an infinite line of charge is true?
• Since this is an infinite line of charge, it doesn’t matter which location is the origin on the line of charge
• The electric field from each element of charge dq ALWAYS lies in the plane of the page, assuming that the observation point is also in the plane of the page.
• The TOTAL electric field from the line of charge will point perpendicular to the line of charge
• The TOTAL electric field from the line of charge will point parallel to the line of charge
• The Total electric field from the line of change should NOT depend on D.
(A) Only 1 statement true (B) two are true (C) three are true (D) only 1 is false (E) none false
Electric Field LinesVector map of electric fieldDirection of field lines indicate local direction of E field (and force on POSITIVE test chargeNumber of lines leaving/ entering a charge proportional to the chargeField lines BEGIN on POSITIVE charges and END on Negative chargesDensity of Field lines proportional to STRENGTH of electric field
Electric Field LinesIn what direction does electric field point at the surface of these conductors?
Note: Field lines from charged conductors reflect the shape of the conductorNote: Electric field “concentrated” by sharp point of object on left. Like a lightning rod.Note: What is the E field INSIDE of the conductor in the picture on the right?