Question

Two point charges $q_{A}=3 \,\mu C$ and $q_{B}=-3 \,\mu C$ are located $20 \,cm$ apart in vacuum. If a negative test charge of magnitude $1.5 \times 10^{-9} C$ is placed at this point, what is the force experienced by the test charge?

• A. $7.2 \times 10^{-3} N$
• B. $8.1 \times 10^{-3} N$
• C. $9.0 \times 10^{-3} N$
• D. $9.6 \times 10^{-3} N$

Answer 1

Answer: (B)

$E_{P}=2\left[\frac{\left(9 \times 10^{9}\right)\left(3 \times 10^{-6}\right)}{0.1^{2}}\right]=5.4 \times 10^{6} N C ^{-1}$
$F_{P}=E_{P^{\prime}} q_{p}=\left(5.4 \times 10^{6}\right)\left(1.5 \times 10^{-9}\right) N =8.1 \times 10^{-3} N$