Metropolitan Transportation Authority (MTA) Electrical Practice Test 2026 – Your All-in-One Guide to Exam Success!

This tests recognizing the device whose magnetic field is produced by electric current in a coil around a soft iron core. When current flows, each turn of the coil generates its magnetic field and these fields combine, while the soft iron core concentrates and strengthens the flux. Because the field exists only with current, you can switch it on and off and adjust its strength by changing the current, the number of turns, or the core. That makes it an electromagnet. A permanent magnet holds its magnetization without current, a general magnet is any device that produces a magnetic field, and a temporary magnet refers to a material that becomes magnetized only while influenced by a field and may lose magnetization when the influence is removed.