问题描述：
英语翻译
26.Magnetic Forces Imagine that a current-carrying wire is perpendicular to Earth’s magneticfield and runs east-west.If the current is east,in which direction is the force on the wire?
27.Deflection A beam of electrons in a cathode-ray tube approaches the deflecting magnets.The north pole is at the top of the tube; the south pole is on the bottom.If you are looking at the tube from the
28.Galvanometers Compare the diagram of a gal- vanometer in Figure 24-18 on page 655 with the electric motor in Figure 24-20 on page 656.How is the galvanometer similar to an electric motor?How are they different?
29.Motors When the plane of the coil in a motor is perpendicular to the magneticfield,the forcesdo not exert a torque on the coil.Does this mean that the coil does not rotate?Explain.
30.Resistance A galvanometer requires 180 µA for full-scale deflection.What is the total resistance of the meter and the multiplier resistorfor a 5.0-V full-scale deflection?
31.
Critical Thinking How do you know that the
forces on parallel current-carrying wires are a
result of magnetic attraction between wires,and not a resultof electrostatics?Hint:Consider whatthe charges are like when the force is attractive.Thenconsider what the forces are when three wirescarry currents in the same direction.
26.Magnetic Forces Imagine that a current-carrying wire is perpendicular to Earth’s magneticfield and runs east-west.If the current is east,in which direction is the force on the wire?
27.Deflection A beam of electrons in a cathode-ray tube approaches the deflecting magnets.The north pole is at the top of the tube; the south pole is on the bottom.If you are looking at the tube from the
28.Galvanometers Compare the diagram of a gal- vanometer in Figure 24-18 on page 655 with the electric motor in Figure 24-20 on page 656.How is the galvanometer similar to an electric motor?How are they different?
29.Motors When the plane of the coil in a motor is perpendicular to the magneticfield,the forcesdo not exert a torque on the coil.Does this mean that the coil does not rotate?Explain.
30.Resistance A galvanometer requires 180 µA for full-scale deflection.What is the total resistance of the meter and the multiplier resistorfor a 5.0-V full-scale deflection?
31.
Critical Thinking How do you know that the
forces on parallel current-carrying wires are a
result of magnetic attraction between wires,and not a resultof electrostatics?Hint:Consider whatthe charges are like when the force is attractive.Thenconsider what the forces are when three wirescarry currents in the same direction.
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