1). There will be one great spark across the terminals of the switch as it closes.
2). Current will start to flow through the wire, from the ( + ) of the left-side battery, all the way around the circuit, through the coils wrapped around the nail, to the ( - ) of the right-side battery.
3). The current will be quite large, because the only resistance in the circuit is a bunch of wire, I = V / R, V is around 3 volts, and the resistance of wire is very low.
4). The magnetic field around the wire due to the current flowing through it will cause the nail to become temporarily magnetized.
5). The batteries will peter out after a comparatively short time, the current will die out, and the nail will become non-magnetic, even if the switch stays closed. The batteries may even be warm, but in any case, they will be toast.
