Question

sir i need help from u actuly making a project iwant to convert 12 volts battery current in to 3 to 5 volts so tell me about the resistoer or which omh resistor required

Answer 1

To use resisters actually waste energy, just use the voltage divider rule
12 R1/(R1 + R2) = 5 it has a thevenin resistance of R1||R2, design the voltage drop across it at maximum current of 2 V.
To preserve energy you can use a transformer and switch the 12 v supply on and off on its input. The process is called an inverter.

Answer 2

Sir, I need to know if any handbook is available relating to household wiring? We would appreciate your response.

C.Ferns

Answer 3

Generally electrical service input into home and wiring have Electrical Code requirements. Do search online or amazon.com. Generally there's a new one every so often. It should have all specifications as to wire sizes and load requirements as well as circuit beakers or fuse. Actually the math is very basic but there's a lot of Codes and that's generally what an Electrician does, it takes time to know the Codes and that is one aspect I didn't like. I preferred electronics where I could set my own specification for the work I was doing.

Answer 4

I would recommending just using a transistor. There are power transistors that would easily do what you desire.