Voltage vs amps

[malta]

Hi all

so i have a question.... i just bought a 'domestic' radio that works off the mains supply (240v) using an AC adapter that converts the power into a dc 12v, with a small amp output (about 0.5). In order to use the radio on the boat, i was going to simply wire a jack (into the a/c socket on the radio) and wire this directly to a cigarette lighter connection, so that it will have access to the boat battery that is 12v - the boat battery has a power (?) rating of 100 amp. If i do this, will the radio work, or will the higher amperage on the battery somehow short the radio, even though its still a 12v supply?

Also, if i somehow wire the connection in the reverse order (positive on the outside and negative on the inside of the power jack, will this simpoly not work, or will i short it? (i have a 50% chance of getting it wrong)

as you can probably see, i am not the world's greatest electrician.

Cliff

 

[Georgesalmon]

Re: Voltage vs amps

The battery will not hurt the radio. It will only draw the amps it needs to function, no more, no matter how big the source is. Make sure you use a fuse( 1 amp or less? ) in the line to the radio. Reversing polarity will likely wreck the radio. The center post is usually pos. Use a meter on the AC adapter to check polarity and find out. Also usually the pos wire has a stripe or groove or bump, or something to indicate which one it is.

 

[tpenfield]

Re: Voltage vs amps

Electrical voltage Resistance & Current relationship . . . V=IR

The radio will only take the amperage that it wants . . . not the 100 amp (or whatever) that the circuit can provide. So, you should be OK

 

[Alumarine]

Re: Voltage vs amps

Usually the A/C adapter will have a diagram on it indicating the polarity of the plug.
But as George said above if you use a meter you should be able to determine that.

 

[malta]

Re: Voltage vs amps

thanks all.

yes the adaptor does have a diagram showing positive to be the centre, and negative on the outside. I'll check to make sure which is which when i wire it up.

v = ir.. that takes me back a few years to school days

thanks again

 

[H20Rat]

Re: Voltage vs amps

check, doublecheck, and then check once more before you plug it in! I've chopped the ends off lots of walwarts and ran straight to a battery, but I've also fried equipment from not following that triple check procedure! 99% of electronics equipment is EXTREMELY unforgiving about reverse polarity, the instant you touch the terminals, the gear is dead.

 

[MH Hawker]

Re: Voltage vs amps

Yep their is only so much smoke in the bottle and if you let it out its gone.