Final answer:
The static magnetic field in a 1.5T MR scanner can induce weak electric currents in a patient's body, potentially leading to various effects. Patients with pacemakers are not given MRIs due to the possible interference with the pacemaker caused by the induced electric currents.
Step-by-step explanation:
The possible effect of the static magnetic field in a patient lying still in a 1.5T MR scanner is the induction of weak electric currents in the body. When a patient is inside the MRI machine, a large magnetic field is generated by the solenoid surrounding the patient. This magnetic field can induce electric currents in the tissues and cells of the body, which can have various effects depending on the specific situation. For example, if a patient has a pacemaker with wires, the magnetic field can induce electric currents in the wires, potentially interfering with the functioning of the pacemaker. This is why patients with pacemakers are not given MRIs. Overall, the effect of the static magnetic field in a patient lying still in a 1.5T MR scanner is the induction of weak electric currents in the body, which can have different consequences depending on the specific circumstances.