When calculating an electric field, first calculate the magnitude and draw a picture, then divide the field into components and use your picture to guide you as to which components are positive and which are negative.
When calculating an electric field associated with two charges, do the above for each charge separately. Then you can get the total electric field by addition, first for one component, then for the other.
Be ready to quickly sketch electric fields for uncomplicated charge distributions ( point charges)
When analyzing circuits, often you have to analyze the whole system to be able to understand one part.
Be ready to describe, analyze and understand the behavior and influence of a capacitor as it charges or discharges in simple circuits.
Be prepared for an essay question that involves a circuit with a capacitor.
i have a question about your point charge calculation in class today. you calculated the E total and then found the Ex and Ey components, adding them together to get the final result as (0,Ey's) if the x components cancelled, etc. However, when you got Ex=(kq)/2a^2, you then multiplied it by cos of theta, which was 45 degrees. So you had Excos(45). This turned out to be 1/sqr rt 2 multiplied by Ex. The cos of 45 degrees however is sqr rt 2 / 2. So did i miss a step or should Excos(45) read instead (kq)(sqr rt 2)/4a^2?
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ReplyDeletei guess you just simplified the sqrt rt 2/2 so there is no rt in the top, and it is the same as 1/ sqrt rt 2. But this still changes the answer by a factor of two and this is why it bugs me... am i missing something?
ReplyDeletefor the problems we did in class, the x and y components were each smaller than the magnitude by 1/sqrt(2)
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