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Electricity and Magnetism

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Using the Elelctric Field to Determine a Mystery Charge

EANDM-26NEUK

You are located an unknown distance from a mystery charge $Q$. By measuring the electrostatic force on a small known test charge you determine that the E-field due to the point charge is $E_1 = 16 \: \frac {\text N}{\text C} $ pointing directly North. You move $2 \: \text m$ further North and measure the E-field again. This time you measure the E-field to be $E_2 = 4 \: \frac {\text N}{\text C} $ again point North.

Using this information determine the value of the mystery charge $Q$.

A

$7.1 \: \text nC$

B

$1.8 \: \text nC$

C

$3.6 \: \text nC$

D

$8.0 \: \text nC$

E

$23 \: \text nC$