V=IxR. How much resistance (in amps) did an adult rat provide in my home made trap?

[mart]

A couple of years ago I had a rat in the loft running between my house and the neighbours in the small hours. Not having much faith in the efficiency of the traps that can be bought, I made one as thus>

Plastic gravel tray about 18”x18”x 2” deep. A piece of mesh in the base of the tray with the negative wire attached. A length of timber fastened along the top edge of the plastic tray. At 3” intervals, nails were protruding through the timber by a about ¾” to attach bait to (something like twix or Mars that adheres well). The live wire attached to the head of a nail (all of which were connected to each other with wire). Probably bout ½” of water in the plastic tray.

In bed, I heard the shaking of the mesh while the rat was sampling the offerings. But, on later inspection the rat had escaped as it were. I assumed that not enough current had been flowing through the circuit for it to work as intended. Maybe if an electric heater or similar had been connected in the circuit it would have worked (dragging more current)? It has just occurred to me that maybe the rat being part of the circuit when it made contact would have been the required “resister” in the circuit, but to what extent I do not know?

How did the rat escape?
What amount of current would have been flowing once the rat became part of the circuit?
What similar devices have the engineers and men in sheds devised?

 

[roofman]

What voltage did it recieve??

 

[mart]

Tips tips

 

[mart]

What voltage did it recieve??

240

 

[dobbslc]

Probably a very lucky rat!
I've seen a few inside fuse boards trucking etc that weren't so lucky......

 

[mr_splatter]

I've had vermin problems myself in the loft and as I don't really like poison or clearing up from a heavy snap trap, I bought a thing called a 'Raticator'. Runs off 4 duracell batteries and they basically wander into the thing and step on two plates. I suspect the voltage is quite high (several thousand volts I suspect due to the arcing if there is any contamination). As above it doesn't take much current to kill them but the volts helps to get it through them. Killed about 35 last year on same set of batteries, put the bodies on the lawn and within the hour the red kites had taken them. None this year as I think I managed to find where they were coming in and blocked it up. Had a CCTV rigged up in loft so I could see the trap from my computer.

 

[rtbcomp]

Having anything else in circuit would make no difference btw

If wired in parallel with ratty.

It would reduce the current going through the rat if wired in series with it. The amount depends on the ratio of the rat's resistance to that of the appliance.

 

[MattH]

Putting another resistor in series with said rat is not going to do anything.

No resistance = dead short and maximum current flowing.

Rat = High resistance and minimum current flowing

Heater element = low resistance and high current flowing

Rat + Heater element = High resistance again and minimum current flowing

I would of had two pieces of mesh, one on the bottom and one 30-40mm above separated with some wood. bottom L, top N. Place the bait on the lower mesh and trust the rat to push itself between the plates!
Rat BBQ.

 

[Paul99]

I worked for a bloke who had made a semi-permanent mouse / squirrel / rat trap set up that was connected to the mains - his was more like the electric fly swatter things you can by where poles were connected to separate layers of mesh insulated from each other by half inch or so - the bait was placed in a tray behind the mesh and as the rodents stretched across the gap to get through and bridged the mesh layers they got zapped - he reckons it only very rarely killed them stone dead - but instead they all just about jumped out of their skin and staggered off - he even had a chair at the kitchen window especially to keep an eye on it. I didn't think it would work but he reckoned that a week or so after turning it on for a few spells having seen mice etc about they would completely disappear and he'd get the tell tale smell in the barn that it had done the job. I still reckon a few old fashioned traps - personally I'd do everything to avoid them dieting inside walls roofs etc but he was happy with it.

 

[Maker]

I'd be surprised if Mr Rat ever went for a swim, get rid of the water and he would probably walk onto the mesh. I would personally replace the mains supply with a rectified supply and some big capacitors (More amps), now Mr Rat will explode (Maybe cover the tray over with something).

 

[roofman]

Would,nt mr rat be better recieving DC voltage just like the electric chair...

 

[Wallace]

A friend did similar using a catering size coffee can with an aluminised inner to catch a mouse in his bedroom, live wire stripped bare with a bit of insulation through a hole in the base and earth to the base. He heard the mouse in the dark and the blue flash nearly blinded him!

 

[roofman]

I can find no reference to the electric chair using direct current - because of Edison

does that mean it was,nt used then...look harder

 

[roofman]

I'm too lazy to look, plus 'everyone' knows AC is more effective for execution purposes than DC

ime led to believe Amps kill and voltage frys...DC amps are the babys for the job getting done

 

[barracuda816]

Deleted due to nonsensical ramblings

 

[Spark plug]

Dc is more dangerous as there is no pulse as with AC, so once you get hold you can't let go.

 

[roofman]

You need voltage to defeat the skin resistance though - a car battery is easily capable of hundreds of amps but you can safely hold both terminals because the voltage is so low.

Aye but a plug lead with 1000,s of volts wont do nothing except make you jump because it has no amps

 

[barracuda816]

Dc is more dangerous as there is no pulse as with AC, so once you get hold you can't let go.

I have had an ac shock and can tell you my muscles wont react quick enough to a 50hz supply (50 times a second).

 

[roofman]

Tell that to a pacemaker user

But, it can make you jump - a battery 'with thousands of amps' can't...

yet again ime out through lack of interest

 

[MattH]

It's all about your natural pacemaker and current path across your heart. Below a certain current range and the pacemaker won't be interupted. Above a certain range and there is a protective clamping action that stops the pacemaker being disrupted. If memory serves the lethal range is something like 120-200ma. Not much at all, but factor is the M Ohms of dry skin resistance and you need a lot of volts to develop that kind of current.
DC and AC make no diference to this apart from causing you to spasm and not release your grip on a conductor.