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Review. Consider a capacitor with vacuum between its large, closely spaced, oppositely charged parallel plates. (a) Show that the force on one plate can be accounted for by thinking of the electric field between the plates as exerting a “negative pressure” equal to the energy density of the electric field. (b) Consider two infinite plane sheets carrying
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Physics for Scientists and Engineers
- Unreasonable results Frustrated by the small Hall voltage obtained in blood flow measurements, a medical physicist decides to increase the applied magnetic field strength to get a 0.500-V output for blood moving at 30.0 cm/s in a 1.50-cm-diameter vessel. (a) What magnetic field strength is needed? (b) What is unreasonable about this result? (C) Which premise is responsible?arrow_forwardExplain why B=0 inside a long, hollow copper pipe that is carrying an electric current parallel to the axis. Is B=0 outside the pipe?arrow_forwardAn electron in a TV CRT moves with a speed of 6.0107 m/s, in a direction perpendicular to Earth's field, which has a strength of 5.0105 T. (a) What strength electric field must be applied perpendicular to the Earth’s field to make the election moves in a straight line? (b) If this is done between plates separated by 1.00 cm, what is the voltage applied? (Note that TVs are usually surrounded by a ferromagnetic material to shield against external magnetic fields and avoid the need for such a collection,)arrow_forward
- Using an electromagnetic flowmeter (Fig. P19.69), a heart surgeon monitors the flow rate of blood through an artery. Electrodes A and B make contact with the outer surface of the blood vessel, which has interior diameter 3.00 mm. (a) For a magnetic field magnitude of 0.040 0 T, a potential difference of 160 V appears between the electrodes. Calculate the speed of the blood. (b) Verify that electrode A is positive, as shown. Does the sign of the emf depend on whether the mobile ions in the blood are predominantly positively or negatively charged? Explain. Figure P19.69arrow_forwardA proton and a helium nucleus (consisting of two protons and two neutrons) pass through a velocity selector and into a mass spectrometer. The radius of the protons circular path is rp. Find an expression for the radius r of the helium nucleuss path in terms of rp. (You may assume the mass of a proton is roughly equal to the mass of a neutron, and the helium nucleus has the same speed as the proton.)arrow_forwardUsing an electromagnetic flowmeter (Fig. P19.69), a heart surgeon monitors the flow rate of blood through an artery. Electrodes A and B make contact with the outer surface of the blood vessel, which has interior diameter 3.00 mm. (a) For a magnetic field magnitude of 0.040 0 T, a potential difference of 160 V appears between the electrodes. Calculate the speed of the blood. (b) Verify that electrode A is positive, as shown. Does the sign of the emf depend on whether the mobile ions in the blood are predominantly positively or negatively charged? Explain. Figure P19.69arrow_forward
- Hall potentials are much larger for poor conductors than for good conductors. Why?arrow_forwardA proton moving in the plane of the page has a kinetic energy of 6.00 MeV. A magnetic field of magnitude H = 1.00 T is directed into the page. The proton enters the magnetic field with its velocity vector at an angle = 45.0 to the linear boundary of' the field as shown in Figure P29.80. (a) Find x, the distance from the point of entry to where the proton will leave the field. (b) Determine . the angle between the boundary and the protons velocity vector as it leaves the field.arrow_forwarda.Find H in rectangular components at P(3,4,2) If there is a current filament on the z axis carrying 5 mA in the az direction. b. Repeat if the filament is located at x = -1, y = 2. (c) c. Find H if both filaments are present.arrow_forward
- For static (time-independent) fields, which of the following current densities are possible? (a) J = 2x²ya, + 4x² z²ay - 6x²y az z² (b) J=ap + cos(Ø) a₂ No one above O b a & b aarrow_forwardQ (t) = 3e-0.7t sin() + 0.01 sin(4t) - 0.02 cos(4t) The function Q defined above models the electric charge, measured in coulombs, inside a lightbulb t seconds after it is turned on. Which of the following presents the method for finding the instantaneous rate of change of the lightbulb's electric charge, in coulombs per second, at time t = 4? Q" (4) = -0.213 A B C D Q'(4) = -0.171 Q(4) Q (0) 4-0 = 0.053 Q (4) = 0.194arrow_forwardA 2.4 m segment of wire supplying current to the motor of a submerged submarine carries 950 A and feels a 3.9 N repulsive force from a parallel wire 5.00 cm away. What is the magnitude of the current in the other wire in A?arrow_forward
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