Waste metal. Electromagnets can be used to separate magnetic materials such as iron and steel from mixed piles of trash. The metals are pulled out by the magnet while nonmagnetic objects such as glass and plastic stay behind.aste metal. Electromagnets can be used to separate magnetic materials such as iron and steel from mixed piles of trash. The metals are pulled out by the magnet while nonmagnetic objects such as glass and plastic stay behind.
The definition of pessimistic is constantly expecting the worst. An example of pessimistic is a person who always believes that something is going to fail. of or characterized by pessimism; expecting the worst.
Optimistic vs. Pessimistic locking. 1  Optimistic Locking is a strategy where you read a record, take note of a version number (other methods to do this involve dates, timestamps or checksums/hashes) and check that the version hasn't changed before you write the record back.