MCAT Physics Question — Electric Field
- Sep 09, 2014
- MCAT Question of the Day
The distance from a point charge is tripled. What is the ratio of the strength of the electric field at the original distance to the strength of the field at the new distance?
The strength of the electric field due to a point charge is given by the relationship: E=kq/r2. If E is the strength of the field at the original location, E’=kq/(3r)2=kq/(9r2). E’=E/9, i.e. E=9E’, and the ratio of the strength of the electric field at the original location to the strength at 3x the distance is 9:1.
a) 9:1, correct.
b) 3:1, incorrect, This would be true only if the E was inversely proportional to the distance, but E is inversely proportional to the distance squared.
c) 1:3, incorrect, This would be true if E was proportional to the distance, but E is inversely proportional to the distance squared.
d) 1:9, incorrect, This would only be true if E was proportional to the distance squared, but E is inversely proportional to the distance squared.
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