A researcher intends to store electrostatic energy by fixing three point charges in space

PHYSICS · Multi-part · A Level · Physics · Fields and their consequences · Fields and their consequences

Problem

A researcher intends to store electrostatic energy by fixing three point charges in space. Two charges,

q_{1}=+3.0\,\mu\text{C}

and

q_{2}=+5.0\,\mu\text{C}

, are already located on the

y

–axis at

(0,\,0.10\,\text{m})

and

(0,\,-0.10\,\text{m})

, respectively. The researcher must now bring a third charge

q_{3}=-4.0\,\mu\text{C}

from infinity to the point

(0.12\,\text{m},\,0)

. (a) Determine the work the researcher must do to bring

q_{3}

from infinity to its final position, with

q_{1}

and

q_{2}

already fixed. (b) Calculate the total electric potential energy of the three–charge system after

q_{3}

is in place. (c) Suppose the researcher instead chose to place

q_{3}

(0.12\,\text{m},\,0.06\,\text{m})

. Without recomputing every numeric value, describe qualitatively whether the magnitude of the required work would increase, decrease, or stay the same, and explain why.

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