Consider a silver wire (σ = 6.3 ✕ 107 ω⁻¹ · m⁻¹) with a cross-sectional area of 1 mm2 (similar to your connecting wires) and carrying 0.3 amperes of current, which is about what you get in a circuit with a round bulb and two batteries in series. calculate the strength of the very small electric field required to drive this current through the wire.