A solenoid is connected to an ac source A copper ring and a

A solenoid is connected to an ac source. A copper ring and a rubber ring are placed inside the solenoid, with the normal to the plane of each ring parallel to the axis of the solenoid. An induced emf appears------. (a) in the copper ring but not in the rubber ring (b) in the rubber ring but not in the copper ring (c) in both rings I selected (a) b/c copper is a good conductor of charges and rubber is an insulator; however, the answer key says (c) is the correct answer. Would anyone care to explain why? Thanks!

Solution

As solenoid is connected to an ac source,so the flux through it changing, there will be induced emf in both rings. since copper is conductor,current flow through the copper ring, But rubber is insulator, according to the law there will be induced emf, but due to it has infinite resistance the current will not flow.