Concept explainers
* EST Generator for space station Astronauts on a space station decide to use Earth’s magnetic field to generate electric current Earth’s
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College Physics
- (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(a) A car generator turns at 400 rpm when 1he engine is idling. Its 300-turn, 5.00 by 8.00 cm rectangular coil rotates in an adjustable magnetic field 50 that it can produce suf?cient voltage even at low rpms. What is the field strength needed to produce a 24.0 V peak emf? (b) Discuss how this required field strength compares to those available in permanent and electromagnets.arrow_forwardA rectangular conducting loop is placed near a long wire carrying a current I as shown in Figure OQS1.3. If I decreases in time, what can be said of the current induced in the loop? (a) The direction of the current depends on the size of the loop. (b) The current is clockwise. (c) The current is counterclockwise. (d) The current is zero. (e) Nothing can he said about the current in the loop without more information.arrow_forward
- In Figure P30.26, a semicircular conductor of radius R = 0.250 m is rotated about the axis AC at a constant rate of 120 rev/min. A uniform magnetic field of magnitude 1.30 T fills the entire region below the axis and is directed out of the page. (a) Calculate the maximum value of the emf induced between the ends of the conductor. (b) What is the value of the average induced emf for each complete rotation? (c) What If? How would your answers to parts (a) and (b) change if the magnetic field were allowed to extend a distance R above the axis of rotation? Sketch the emf versus time (d) when the field is as drawn in Figure P30.26 and (e) when the field is extended as described in part (c). Figure P30.26arrow_forward(a) If the emf of a coil rotating in a magnetic field is zero at t = 0, and increases to its first peak at t = 0.100 ms, what is the angular velocity of the coil? (b) At what time will its next maximum occur? (c) What is the period of the output? (d) When is the output first one-fourth at its maximum? (e) When is it next one-fourth at its maximum?arrow_forwardReview. In Figure P30.42, a uniform magnetic field decreases at a constant rate dB/dt = K, where K is a positive constant. A circular loop of wire of radius a containing a resistance R and a capacitance C is placed with its plane normal to the field. (a) Find the charge Q on the capacitor when it is fully charged. (b) Which plate, upper or lower, is at the higher potential? (c) Discuss the force that causes the separation of charges. Figure P30.42arrow_forward
- An N-turn circular wire coil of radius r lies in the xy-plane (the plane of the page), as in Figure P20.10. A uniform magnetic field is turned on, increasing steadily from 0 to B0 in the positive z-direction in t seconds. (a) Find a symbolic expression for the emf, , induced in the coil in terms of the variables given. (b) looking down on at the xy-plane from the positive z-axis, is the direction of the induced current clockwise or counterclockwise? (c) If each loop has resistance R, find an expression for the magnitude of the induced current, I.arrow_forwardA 50-turn rectangular coil with dimensions 0.15m0.40m rotates in a uniform magnetic field of magnitude 0.75 T at 3600 rev/min. [a) Determine the emf induced in the coil as a function of time, (b) If the coil is connected to a 1000 resistor, what is the power as a function of time required to keep the coil turning at 3600 rpm? (c) Answer part (b) if the coil is connected to a 2000 resistor.arrow_forwardAn N-turn circular wire coil of radius r lies in the xy-plane (the plane of the page), as in Figure P20.10. A uniform magnetic field is turned on, increasing steadily from 0 to B0 in the positive z-direction in t seconds. (a) Find a symbolic expression for the emf, , induced in the coil in terms of the variables given. (b) looking down on at the xy-plane from the positive z-axis, is the direction of the induced current clockwise or counterclockwise? (c) If each loop has resistance R, find an expression for the magnitude of the induced current, I.arrow_forward
- A square, flat loop of wire is pulled at constant velocity through a region of uniform magnetic field directed perpendicular to the plane of the loop as shown in Figure OQ31.5. Which of the following statements are correct? More than one statement may be correct. (a) Current is induced in the loop in the clockwise direction. (b) Current is induced in the loop in the counterclockwise direction. (c) No current is induced in the loop. (d) Charge separation occurs in the loop, with the top edge positive. (e) Charge separation occurs in the loop, with the top edge negative. Figure OQ31.5arrow_forwardTranscranial magnetic stimulation (TMS) is a noninvasive technique used to stimulate tedious of the human brain (Figure P31.3). In TMS, a small coil is placed on the scalp and a brief burst of current in the coil produces a rapidly changing magnetic field inside the brain. The induced emf can stimulate neuronal activity. (a) One such device generates an upward magnetic Held within the brain that rises from zero to 1.50 T in 120 ms. Determine the induced emf around a horizontal circle of tissue of radius 1.60 mm. (b) What If? The field next changes to 0.500 T downward in 80.0 ms. How does the emf induced in this process compare with that in part (a)? Figure P31.3 Problems 3 and 51. The magnetic coil of a Neurostar TMS apparatus is held near the head of a patient.arrow_forwardAn astronaut is connected to her spacecraft by a 25-m-long tether cord as she and the spacecraft orbit Earth in a circular path at a speed of 3.0 105 m/s. At one instant, the voltage measured between the ends of a wire embedded in the cord is measured to be 0.45 V. Assume the long dimension of the cord is perpendicular to the vertical component of Earths magnetic field at that instant. (a) What is the magnitude of the vertical component of Earths field at this location? (b) Does the measured voltage change as the system moves from one location to another? Explain.arrow_forward
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