Final answer:
An inverter is an apparatus that converts alternating current (AC) to direct current (DC). It is used to change the AC power supplied by the electrical grid into the DC power needed by devices like cell phones and cars.
Step-by-step explanation:
An inverter is an apparatus that converts alternating current (AC) to direct current (DC). When it comes to electrical power, most appliances and devices in our homes operate on AC. However, certain devices, like computers, cell phones, and cars, require DC to function. This is where an inverter comes in. It changes the AC power supplied by the electrical grid into the DC power needed by these devices.
For example, imagine you want to charge your cell phone. The charger you plug into the wall socket includes an inverter that transforms the AC voltage from the socket into DC voltage to charge your phone's battery. This way, the inverter ensures a steady flow of DC current to charge your device.
Therefore, the correct answer to the question is d) inverter.