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Human life needs energy. The following energy is mainly produced by chemical changes A. The heat required by electric kettle to boil water B. the electric energy generated by hydropower station using hydraulic power c. the heat energy generated by the burning alcohol lamp D. the wind energy used by wind power station
A. B. there is no new material in the process of hydroelectric power generation, which is a physical change; C. alcohol combustion can generate water and carbon dioxide, which is a chemical change; d. There is no new material in the process of wind power generation, which is a physical change Item error. So select C
Please use the switch and bulb shown in the figure to connect with the electric iron to form a circuit. Requirements: after the electric iron is powered on, the working temperature of the switch in the closed state is higher than that of the switch in the off state
The switch is connected in parallel with the light bulb. When the switch is closed, the light bulb is short circuited, and only the electric iron works independently in the circuit. When the switch is closed, the light bulb is connected in series with the electric iron, so the voltage shared by the light bulb is small, and the power is small, so the working temperature of the switch in the closed state is higher than that of the switch in the open state
When the electric iron is electrified, the temperature is very high, but the wire connecting the electric iron is not very hot, because ()
A conductor is protected by insulating layer, which can insulate heat
B the current through the wire is less than the current through the iron
C wire dissipates heat quickly, so the temperature is low
The resistance of D wire is small, so is the heat generated
The resistance of D wire is small, so is the heat generated
Obviously
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