# Illustration Faraday cage and electric field

Here you see a so called Faraday cage. It is a conducting hollow box in an external electric field $$E$$. Since the box is conductive, electrons can move freely on its surface. In an electric field, the electrons move opposite to the direction of the external field (this effect is called electrostatic induction). On the other side of the box there is electron deficiency, therefore this side is positively charged.