If you were provided with three black painted metal rods, one of which is known to be made of brass, one of magnetised steel and one of unmagnetised steel, describe how, without scratching the black paint, you would identify each of the rods.
You have three black painted metal rods. One is made of brass, one of magnetised steel and one of unmagnetised steel. Describe how to find out what each rod is made of. You must not scratch the black paint.