They saw a haunted house in the wood.
noun or verb

That would be a noun because it's a person stating it.

3 is blunder, i’m not sure about the last one but the first two look correct

the direction of the magnetic field produced by an electric current will change when the direction of the electric current changes. for example : if a current is flowing in a straight length of wire, the magnetic field is described by a concentric circle (using right-hand rule).