Michigan Test for Teacher Certification (MTTC) Secondary Integrated Science Practice test

Which method is NOT effective for strengthening an electromagnet?

1. Using more battery power

2. Adding more coils

3. Using a wooden core

4. Inserting an iron core

The correct answer is: Using a wooden core

The method that is not effective for strengthening an electromagnet involves using a wooden core. In electromagnet design, the strength of the magnetic field generated is significantly enhanced by using materials with high magnetic permeability, such as iron. Iron has properties that allow it to be magnetized easily, thus amplifying the magnetic field created by the coil of wire wrapped around it. On the other hand, wood is a non-magnetic material; it does not conduct magnetic lines of force and therefore does not contribute to the strength of the electromagnet. Using a wooden core would not enhance the magnetic field and may even allow it to be weaker compared to an electromagnet using a ferromagnetic core. Increasing battery power, adding more coils, and inserting an iron core are all effective ways to strengthen an electromagnet. More battery power increases the current flowing through the coils; more coils increase the total length of wire carrying current, which increases the magnetic field; and an iron core significantly boosts the magnetic field strength due to its ferromagnetic properties.