Can a dead car battery be completely recharged by just jump starting the car and driving around?
Yes, but it depends on what you mean by "dead." A car battery is a rechargeable battery. In common usage dead simply means discharged. Once the engine is running it drives an alternator that recharges the battery. There is probably some misunderstanding because people think of batteries like the ones in a flashlight or toy, which are usually not rechargeable, so must be replaced with fresh ones after they run down. The main reason for a battery in a car is to provide energy to the starter motor to start the engine. That takes a fair amount of energy, but since the battery is rechargeable, unless there's a problem with the wiring connections or with the charging system, it is quickly recharged once the engine starts. However, no rechargeable battery invented so far will last indefinitely. They are all based on a reversible electrochemical process, but there are other non-reversible chemical processes that will eventually degrade the battery's ability to take and hold a charge. With automotive lead-acid flooded cell batteries, the useful life is about 4-8 years, depending on the design and quality of materials and manufacture. When it will no longer hold enough charge to reliably start the engine, it's time to replace the battery. Lead-acid batteries deteriorate much faster when discharged due to a chemical process called sulfation, a non-reversible chemical reaction. Sulfation causes deposits on the battery's lead plates that increase internal resistance and interfere with the ability to take a charge. Sulfation happens much more quickly when the battery is discharged than when it is fully charged. That's why it's important to check your charging system if your battery seems to be pooping out. A weak or marginal charging system leads to battery sulfation and premature failure.
Is it safe to cut a live wire? What are the implications?
No. You don’t know where that wire is transporting power to. Read all the answers, but also consider that the power could be going to an inductive load, or other reactive load which stores energy. Cutting the live wire could result in a high voltage discharge, which can be harmful to you or equipment on the circuit.What you’re doing when you cut a live wire is exactly what a switch does, but a switch’s housing is grounded (earth), and well insulated.When dealing with electricity, always err on the side of caution.Another danger is that you are exposing a live wire by cutting through the insulation. Why would you even consider doing that?Basically, cutting a live wire can be likened to taking off your helmet while riding your motorbike on the highway at 120 km/h and throwing it away. Taking it off is risky because you’re taking your concentration off the riding. You also lose vision for a brief moment. Then, when the helmet comes off, the wind might catch it and pull you off the bike. If you happen to crash after taking off your helmet, you’re dead. When you throw the helmet away, you may kill or seriously injure someone else. It would be a great idea to stop as soon as possible after taking it off (analogous to turning off power ASAP), and if so, it would have been better to have stopped before taking off the helmet. In addition, you’re not going to stop, take off your helmet, and then ride again; what purpose would that serve?*whispering* That said, it should be safe if your cutter is insulated and you are wearing rubber gloves, and you’re working on anything 240VAC or less… That sure would be an irresponsible answer, but it must be said.
Hermit crabs? (again...)?
Sounds like a surface molt to me. If you have an iso tank with proper conditions then move him into it. If not then do the 2 liter bottle isolation method. Take a 2 liter bottle remove the cap cut the bottom off and stick it down in your sand so the molting crab is isolated from the others. Wouldn't hurt to put 2 small shells of fresh and salt water and some honey with cuttlebone and spiralina powder for energy.