Question
Which type of core material decreases inductance when inserted into a coil?
Answer Options
- A) Ceramic
- B) Brass
- C) Ferrite
- D) Aluminum
Correct Answer: B
Explanation
Inductance is a measure of how easily a magnetic field can be established in a coil’s core. Most materials, like ferrite, powdered iron, and even air, have a relative permeability of 1 or greater, which increases the inductance. However, certain non-magnetic, conductive materials exhibit a permeability of less than 1 relative to air.
Brass (an alloy of copper and zinc) is one such non-magnetic but conductive material. When a slug of brass is inserted into the core of a coil, the eddy currents induced in the brass create a counter-magnetic field that opposes the coil’s own magnetic field. This negative effect reduces the net magnetic flux and consequently decreases the inductance of the coil, which is a property often used for fine-tuning RF coils.
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