UPS2000-G is an online double-conversion UPS. In normal working state: the AC power provides energy, the rectifier converts AC power into DC power, the inverter converts the rectified DC power into pure AC power and provides it to the load, and the charger charges the battery pack.

UPS5000-E is a high-efficiency UPS. Which of the following statements is correct? (Multiple choice)

When it is necessary to stop the running equipment, directly disconnect the isolating switch to cut off the power supply of the equipment.

Compared with the horizontal air supply of row-level air conditioners, upward air supply is more suitable for data centers with lower single cabinet power density.

In a circuit with resistance and capacitance, if the frequency of the current increases from 50 Hz to 100 Hz, how will the impedance of the circuit change?