Consider the Hall effect experiment in Figure P20.67 and suppose the current is carried by electrons. In Section 20.6, we saw that the magnetic field exerts a force on the moving electrons directed from the bottom edge of the wire toward the top. This force causes a net negative charge to accumulate along the top edge, leaving a net positive charge along the bottom. The result is an electric field (called the Hall field) directed from bottom to top. The Hall field opposes the magnetic force on the electrons. The edge charge will grow until the electric force from the Hall field balances the magnetic force. Use this fact to calculate the magnitude of the Hall field. Express your answer in terms of the drift speed v of the electrons and the magnitude B of the magnetic field.

-e -e Figure P20.67