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--- 184_notes:examples:week2_electric_potential_positive_point [2018/01/22 01:37] – tallpaul
+++ 184_notes:examples:week2_electric_potential_positive_point [2018/05/17 16:48] (current) – curdemma
@@ Line 1: / Line 1: @@
-===== Electric Potential from a Positively Charged Balloon =====
+[[184_notes:pc_potential|Return to Electric Potential]]
-Suppose we have a positively charged balloon with total charge  $Q=5\cdot 10^{-9} \text{ C}$ . What is the electric potential at a point  $P$ , which is a distance  $R=50 \text{ cm}$  from the center of the balloon?
+===== Example: Electric Potential from a Positively Charged 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 13: / Line 14: @@
 </WRAP>
-{{ 184_notes:2_potential_positive_balloon.png?150 |Charged Balloon, and Point P}}
+[{{ 184_notes:2_potential_positive_balloon.png?150 |Charged Balloon, and Point P}}]
 ===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