: Một thanh kim loại chiều dài nằm ngang có thể trượt không ma sát trên hai thanh ray bên dưới như trong hình bên. Tác dụng một lực N lên thanh làm cho nó chuyển động đều với vận tốc 2,0 m/s trong từ trường có chiều như hình vẽ. Xác định: a) Cường độ dòng điện chạy qua điện trở

b) Công suất tỏa nhiệt trên điện trở.

c) Công suất của lực .

Currents in dc transmission lines can be 100 a or higher. some people are concerned that the electromagnetic fields from such lines near their homes could pose health dangers. for a line that has current 150 a and a height of 8.0 m above the ground, what magnetic field does the line produce at ground level? express your answer in teslas and as a percentage of the earth’s magnetic field, which is 0.50 g. is this value cause for worry?

Resistivity of a material is the resistance of a cm long sample of the material of 1 cm2 cross-sectional area.

9. an object is moved from the outdoors, which is at a temperature of 100 ºf, to a room at a temperature of 70 º f. what happens to the object when it’s placed in the room with a lower temperature? the object gives off more energy than it absorbs until it reaches a new lower thermal equilibrium where the amount of energy absorbed and given off is the same. the object gives off the same amount of energy as it absorbs until it reaches a new lower thermal equilibrium where the amount of energy given off is greater than the amount of energy it absorbs. the object gives off more energy than it absorbs until it reaches a new higher thermal equilibrium where the amount of energy absorbed and given off is the same. the object absorbs more energy than it gives off until it reaches a new lower thermal equilibrium where the amount of energy absorbed and given off is the same.