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As shown in the figure, the uniform electric field in a certain space is vertically downward, the uniform magnetic field is vertically inward, and a metal bar AB falls freely from high h, then () A. A end first landing B. B end first landing C. both ends simultaneously landing D. the above statements are not correct
According to the rule of the right hand, the b-end is positively charged, and the a-end is negatively charged, so the b-end is subject to the downward electric field force, and the a-end is subject to the upward electric field force, so the b-end falls to the ground first
As shown in the figure, there is a fixed smooth U-shaped metal frame on the horizontal plane, and a metal rod AB is placed on the frame. There is a uniform magnetic field in the direction perpendicular to the paper surface. The following situation may be ()
A. If the direction of the magnetic field is perpendicular to the paper outward, and the magnetic induction increases, the rod AB will move to the right B. if the direction of the magnetic field is perpendicular to the paper outward, and the magnetic induction decreases, the rod AB will move to the right C. if the direction of the magnetic field is perpendicular to the paper inward, and the magnetic induction increases, the rod AB will move to the right D If the direction of the magnetic field is perpendicular to the paper surface and the magnetic induction decreases, the rod AB will move to the right
A. If the direction of the magnetic field is perpendicular to the paper surface outward, and the magnetic induction intensity increases, the magnetic flux through the closed circuit increases. In order to prevent the increase of the magnetic flux, according to Lenz's law, the rod AB will move to the left, so a is wrong; B. If the direction of the magnetic field is perpendicular to the paper surface outward, and the magnetic induction intensity decreases, the magnetic flux through the closed circuit increases
As shown in the figure, there is a fixed smooth U-shaped metal frame on the horizontal plane, and a metal rod AB is placed on the frame. There is a uniform magnetic field in the direction perpendicular to the paper surface. The following situation may be ()
A. If the direction of the magnetic field is perpendicular to the paper outward, and the magnetic induction increases, the rod AB will move to the right B. if the direction of the magnetic field is perpendicular to the paper outward, and the magnetic induction decreases, the rod AB will move to the right C. if the direction of the magnetic field is perpendicular to the paper inward, and the magnetic induction increases, the rod AB will move to the right D If the direction of the magnetic field is perpendicular to the paper surface and the magnetic induction decreases, the rod AB will move to the right
A. If the direction of the magnetic field is perpendicular to the paper surface outward, and the magnetic induction intensity increases, the magnetic flux through the closed circuit increases. In order to prevent the increase of the magnetic flux, according to Lenz's law, the rod AB will move to the left, so a is wrong; B. If the direction of the magnetic field is perpendicular to the paper surface outward, and the magnetic induction intensity decreases, the magnetic flux through the closed circuit decreases, which is to prevent the decrease of the magnetic flux, According to Lenz's law, rod AB will move to the right, so B is correct; C. if the magnetic field direction is perpendicular to the paper surface and inward, and the magnetic induction intensity increases, the magnetic flux through the closed circuit increases; in order to prevent the increase of magnetic flux, according to Lenz's law, rod AB will move to the left, so C is wrong; D. if the magnetic field direction is perpendicular to the paper surface and inward, and the magnetic induction intensity decreases, it will pass through the closed circuit In order to prevent the decrease of the magnetic flux, according to Lenz's law, the rod AB will move to the right, so D is correct
RELATED INFORMATIONS
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- 2. A rectangular granite is 10 meters high, 3 meters wide and 2 meters thick, with a density of 2.5 x 10 cubic kilogram per cubic meter. The maximum bearing capacity on the ground is
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- 6. Is a giraffe the tallest animal on land, or an elephant?
- 7. Giraffe is the tallest animal on the earth at present, so its blood pressure is also the highest among the animals. The average height of an adult giraffe can reach 4.3m, its mass can reach 2T, and the landing area of one sole of a giraffe is 250cm2? (2) If the blood density of a giraffe is 1.05 × 103kg / m3, when its heart contracts, it is necessary to press the blood to the head 3M higher than the heart, then at least how much pressure should be produced when the giraffe's heart contracts? (systolic pressure refers to the pressure produced when the heart contracts. Atmospheric pressure is not taken into account in calculation. In this problem, G is taken as 10N / kg.)
- 8. Which one is more dense, granite or basalt?
- 9. To the south of the park, a 15 meter long, 24 centimeter wide and 3 meter high wall will be built. If 525 bricks are used per cubic meter, how many bricks are used in this wall?
- 10. A stone tablet, 50 m long, 20 cm wide, 3 m high and 75 t in mass, is of high density____ Kg / m3? RT
- 11. As shown in figure a, the smooth parallel guide rails Mn and PQ are placed horizontally without resistance. The distance between the two guide rails is d = 10cm. The conductor rods AB and CD are placed on the guide rails and perpendicular to the guide rails. The resistance of each rod between the guide rails is r = 1.0 Ω. The two rods are tied with insulated wire with length of L = 20cm. When the whole device is in a uniform magnetic field. T = 0, the magnetic field direction is vertical and downward, and the wire is just in the ungrounded position After that, the change of magnetic induction intensity B with time t is shown in Fig. B. the influence of the induced current magnetic field is not taken into account. The whole process of the wire is not broken
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