& BIO EST Magnetic field and brain cells Suppose a power line produces a
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- Eddy current are induced currents set up in a piece of metal when it moves through a nonuniform magnetic field. For example, consider the flat metal plate swinging at the end of a bar as a pendulum, as shown in Figure CQ20.9. (a) At position 1, the pendulum is moving from a region where there is no magnetic field into a region where the field B is directed into the paper. Show that at position 1 the direction of the eddy current is counterclockwise. (b) At position 2, the pendulum is moving out of the field into a region of zero field. Show that the direction of the eddy current is clockwise in this case. (c) Use right-hand rule number 2 to show that these eddy currents lead to a magnetic force on the plate directed at shown in the figure. Because the induced eddy current always produces a retarding force when the plate enters or leaves the field, the swinging plate quickly comes to rest. Figure CQ20.9arrow_forwardUnreasonable results To construct a non-mechanical water meter, a 0.500-T magnetic field is placed across the supply water pipe to a home and the Hall voltage is recorded, (a) Find the flow rate through a 3.00-cm-diameter pipe if the Hall voltage is 60.0 mV. (b) What would the Hail voltage be for the same flow rate through a 10,0-cm- diameter pipe with tire same field applied?arrow_forwardCalculate the Hall voltage induced on a patient’s heart while being scanned by an MRI unit. Approximate the conducting pain on the heart wall by a wire 7.50 cm long that moves at 10.0 cm/s perpendicular to a 1.50T magnetic field.arrow_forward
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- Inductive charging is used to wirelessly charge electronic devices ranging front toothbrushes to cell phones. Suppose the base unit of an inductive charger produces a 1.00 103-T magnetic Held. Varying this magnetic Held magnitude changes the flux through a 15.0-turn circular loop in the device, creating an emf that charges its battery. Suppose the loop area is 3.00 104 m2 and the induced emf has an average magnitude of 5.00 V. Calculate the time required for the magnetic field to decrease to zero from its maximum value.arrow_forwardWhen a magnet is thrust into a coil as in Figure 23.4(a), what is the direction of the louse exerted by the coil on the magnet? Draw a diagram showing the direction of the current induced in the coil and the magnetic field it produces, to justify your response. How does the magnitude of the force depend on the resistance of the galvanometer?arrow_forward(a) An MRI technician moves his hand from a region of very low magnetic field strength into an MRI scanner's 2.00 T field with his fingers pointing in the direction of the field. Find the average emf induced in his wedding ling, given its diameter is 2.20 cm and assuming it takes 0.250 s to move it into the field. (b) Discuss whether this current would significantly change the temperature of the ring.arrow_forward
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