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Question

Physics Question on Electric Charge

What are the units of K=14π0\frac{1}{4\pi\,\in_0}

A

C2N1m2C^2 \, N^{ - 1} \, m^{ - 2}

B

Nm2C2 Nm^2 C^{ - 2 }

C

Nm2C2Nm^2 C^2

D

Unitless

Answer

Nm2C2 Nm^2 C^{ - 2 }

Explanation

Solution

By Coulomb's law F = 14πε0q1q2r2\frac{ 1}{ 4 \pi \varepsilon_0 } \frac{ q_1 q_2 }{ r^2 } k=14πε0=Fr2q2\therefore k = \frac{ 1}{ 4 \pi \varepsilon_0 } = \frac{ Fr^2 }{ q^2 } \hspace20mm (ifq1=q2=q)( if \, q_1 = q_2 = q ) Hence, units of k Nm2C2\frac{ Nm^2 }{ C^2 } = Nm2C2Nm^2 C^{ - 2}