Correct Answer - Option 4 : All of the above
Direct current or DC is needed in equipment that uses any type of battery or cells. These cells can be solar-powered or rechargeable like power banks.
Telephones:
- It consists of a diaphragm that converts energy from our voice into electrical energy that flows through the cables
- It uses a DC voltage of about 50 - 60 V to power the electronic circuitry inside the telephone and AC line to ring the bell.
Relays:
- They are used to change the contacts of the switch from NO (normally open) to NC (normally close) and the spring takes it back to NO (normally open).
- Works on the principle of electromagnetic induction. A solenoid is energized by the DC current which attracts the switch contacts.
- For car accessories and motor vehicles, generally, 12 V batteries are used to supply power to the relay.
Time switches:
- A Timer is a control device that outputs a signal at a preset time after an input signal is received i.e. delays the output signal
- In other way time, switches are basically a battery-powered timer that switches on or off a switch at particular intervals.
- Used in fountains, car ceiling lights television sets, etc. which sleeps after some preset duration of inactivity.
Hence, all the above equipment uses DC.
