Magnetic Resonance Imaging (MRI) Practice Test

In a superconducting magnet, how is the magnetic field strength increased?

1. Increasing the cooling temperature

2. Reducing the size of the coils

3. Increasing the turns of wire

4. Using a stronger power supply

The correct answer is: Increasing the turns of wire

In a superconducting magnet, increasing the magnetic field strength is primarily achieved by increasing the turns of wire in the coils. This principle is based on Ampère’s law, which states that the magnetic field produced by a current-carrying conductor is directly proportional to the current and the number of turns of wire. By adding more wire turns, the total length of the coil increases, allowing for the generation of a stronger magnetic field for the same amount of current. Additionally, superconducting materials allow for significant current flow without resistance when cooled below their critical temperature, further enhancing the magnetic field strength in conjunction with the number of wire turns. This characteristic is critical in MRI technology, where strong and stable magnetic fields are essential for high-quality imaging. The other options do not effectively increase the magnetic field strength. Increasing the cooling temperature would reduce superconductivity and lead to resistance, while reducing the size of the coils would limit the volume of the magnetic field generated. Using a stronger power supply could increase current, but without a corresponding increase in the number of turns, it wouldn't be as effective in achieving a stronger field in a superconducting context.