For example, some fans need 12V voltage, but the current is only 0.5A, the power is 6W, some fans only need 5V, but the current is 1.2A Now the question is how to control the voltage and current. Another is how to change the 220 V AC into 5 V output without heating Add 100 points after explanation And then there is the adjustment of the fan gear. It should not use the rheostat to divide the voltage. Is it to directly lower the voltage to make the current smaller? The power smaller? Is it slow? I mean, how do I do it for a fan? The same power can have different voltages and currents. Of course, I hope that the voltage is high and the current is low. Can I make a 220 V voltage with 0.01 a current How does the AC / DC module work

For example, some fans need 12V voltage, but the current is only 0.5A, the power is 6W, some fans only need 5V, but the current is 1.2A Now the question is how to control the voltage and current. Another is how to change the 220 V AC into 5 V output without heating Add 100 points after explanation And then there is the adjustment of the fan gear. It should not use the rheostat to divide the voltage. Is it to directly lower the voltage to make the current smaller? The power smaller? Is it slow? I mean, how do I do it for a fan? The same power can have different voltages and currents. Of course, I hope that the voltage is high and the current is low. Can I make a 220 V voltage with 0.01 a current How does the AC / DC module work

The high and low of the rated voltage depends on the application, and the rated current depends on the rated voltage and power. I don't understand what you said. The simplest way to control the voltage is to use a transformer. The current depends on the design of the motor, and the iron consumption and copper consumption of the motor

The following statement is correct ()
A. Electric current can convert electric energy into mechanical energy by doing work through electric motor. B. electric current can convert electric energy into internal energy by doing work through electric cooker. C. electric current can convert mechanical energy into electrical energy by doing work through electric fan. D. electric current can convert electrical energy into mechanical energy by doing work through generator
E: [missing option]
F: [missing option]
G: [missing option]

When a current passes through the motor, due to the strong effect of the magnetic field on the current, the motor will rotate and convert the electric energy into mechanical energy. This option is correct; when B current passes through the electric cooker, the heating wire heats the food and converts the electric energy into internal energy

For a motor, the holding current is 2a and the releasing current is 0.6A. What is the mechanical efficiency of converting electrical energy into mechanical energy?

Resistance R
If the current is 2a, then the voltage is 2R
Release the voltage unchanged
Total power U * I = (2a) * r * (0.6A)
Heat loss I ^ 2 * r = (0.6A) ^ 2 * r
Efficiency = (total power - heat loss) / total power = 70%