At the centre of a half ring of radius $\mathrm { R } = 10 \mathrm {~cm}$ and linear charge density $4 \mathrm { nCm } ^ { - 1 }$, the potential is $x \pi \mathrm {~V}$. The value of $x$ is $\_\_\_\_$
At the centre of a half ring of radius $\mathrm { R } = 10 \mathrm {~cm}$ and linear charge density $4 \mathrm { nCm } ^ { - 1 }$, the potential is $x \pi \mathrm {~V}$. The value of $x$ is $\_\_\_\_$