Three metal cores, P, Q and R, each of a different metal, are put inside identical wire coils. At least one of the metals is non-magnetic. The cores are suspended above some iron nails. The three diagrams illustrate what happens when current flows in the coils. The three diagrams below illustrate what happens after the current is switched off. Which core metals are magnetic?
- AP only
- BR only
- CP and Q
- DQ and R