Smoke alarms have many different designs. A common one is powered by a single 9 volt battery but I have also seen ones powered by two AA cells (total 3 volts). Almost any voltage might be used that can be supplied by groups of common 1.5 volt dry cells connected in series.
The volts on cordless drills are based on the battery power. The volt rating reflects the battery that is in the drill.
9.2 volts
You would need to use a voltage converter or transformer that can take in 110 volts and output 220 volts. Make sure the converter is rated to handle the power requirements of the digital alarm clock. Additionally, check the compatibility of the plug to ensure it fits the socket of the digital alarm clock.
It depends on your city's fire codes, most likely yes. "Wired" alarms could either mean "wired to AC power" or "wired to an alarm panel" or both. Start by calling your local fire alarm installer or electrician. Assuming that the detectors are wired to a central hub in the house/building (fire alarm control panel), the panel would normally have a battery back-up installed. For individual units wired to AC, having a battery back up would be safer, no matter what the laws. Some units will automatically remind you when the battery is low, even though the unit is on AC power, since the smoke alarm must continue to function if power is off for some reason.
This could be general smoke alarms installed in you house. This could also be a full functioning fire alarm system. Where you have call points, smoke/heat detectors, bells/sounders/strobes etc. This would be connected through a control panel. SOme intruder alarm systems also facilitate smoke detectors and act as a fire alarm system as well as an intruder alarm system. Or you could make your own fire alarm. With a light switch, call point, smoke/heat detector with a low voltage (12-24 Volts) power adapter/batteries. Although this could not be very reliable. So try and go for the options above.
Divide Watts by Volts ; this gives you Amps.
230 volts
Power = voltage times current, and the power loss is the loss in the line, I^2 * R. At 11,000 volts, the current will be (11,000 / 415 = ) 3.77% of what it is at 415 volts. So the power loss in the line at 11,000 volts will be (3.77% ^2 = ) .14% of what it is at 415 volts.
Volts cause current to flow through the load. The current is measured in amps, and the volts multiplied by the amps gives the power in watts.
There is no particular standard for batteries in fire alarms (or smoke alarms). They may be sealed and non-replaceable (you dispose of the entire unit after ten years); or 9-volt radio batteries, or AA-size alkaline cells, or similar. In a fire-alarm control panel the battery backup unit is often a sealed lead-acid battery (12 volts or 24 volts), which must also be replaced from time to time.
You require about 24 volts to power the windshield wiper.
Ryobi is a brand of power tools that are cordless, meaning battery operated. The 18v stands for 18 volts and offers more torque power for the tools. If you are purchasing a replacement batty I recommend staying with the same manufacturing and voltage of the equipment you have now to make sure it will work in your equipment.