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A small positive test charge is placed at a point in space near a charge distribution, and the force on it is measured. How is the electric field at that point defined from this measurement?
AThe test charge's own charge divided by the force on it
BThe force on the test charge divided by the test charge's own charge
CThe force on the test charge multiplied by the test charge's own charge
DThe force on the test charge divided by the distance to the source
Answer & Solution
Correct answer: B. The force on the test charge divided by the test charge's own charge
1. The electric field is defined as force per unit charge.
2. That means the force measured on the test charge is divided by the size of the test charge itself.
3. Multiplying instead of dividing, or dividing by distance instead of charge, does not match the stated force-per-charge definition.
_Source: OpenStax Physics (CC BY 4.0), Ch 18 "Static Electricity", section 18.3 Electric Field_
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