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--- 184_notes:examples:week2_electric_potential_positive_point [2018/01/24 16:49] – tallpaul
+++ 184_notes:examples:week2_electric_potential_positive_point [2018/01/24 17:43] – [Solution] tallpaul
@@ Line 1: / Line 1: @@
 ===== Electric Potential from a Positively Charged Balloon =====
-Suppose we have a positively charged balloon with total charge $Q=5\cdot 10^{-9} \text{ C}$. What is the electric potential (also called voltage) at a point $P$, which is a distance $R=50 \text{ cm}$ from the center of the balloon?
+Suppose we have a positively charged balloon with total charge $Q=5.0\cdot 10^{-9} \text{ C}$. What is the electric potential (also called voltage) at a point $P$, which is a distance $R=50 \text{ cm}$ from the center of the balloon?
 ===Facts===
-  * The balloon has total charge $Q=5\cdot 10^{-9} \text{ C}$.
+  * The balloon has total charge $Q=5.0\cdot 10^{-9} \text{ C}$.
   * The point $P$ is a distance $R=50 \text{ cm}$ away from the center of the balloon.
   * The electric potential due to a point charge can be written as $$V = \frac{1}{4\pi\epsilon_0}\frac{q}{r},$$ where $q$ represents the charge and $r$ is the distance.
@@ Line 17: / Line 17: @@
 ===Goal===
   * Find the electric potential at $P$.
-===Approximations & Assumptions===
-  * The balloon's electric field outside the balloon acts like a point charge centered at the center of mass of the balloon.
-  * The electric potential infinitely far away from the balloon is $0 \text{ V}$. Read [[184_notes:superposition#Superposition_of_Electric_Potential|here]] for why this is important.
 ====Solution====
+<WRAP TIP>
+=== Approximation ===
+We approximate the balloon as a point charge. We do this because we have the tools to find the electric potential from a point charge. This seems like a reasonable approximation because the balloon is not too spread out, and we are interested in points outside the balloon. so the balloon might "look" like a point charge from the perspective of an observation location that is little far away.
+</WRAP>
+<WRAP TIP>
+=== Assumption ===
+The electric potential infinitely far away from the balloon is $0 \text{ V}$. /*Read [184_notes:superposition#Superposition_of_Electric_Potential|here]] for why this is important.*/
+</WRAP>
 The electric potential at $P$ is given by