Melting a nail with high currents

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In summary, "Melting a nail with high currents" involves passing a significant electrical current through a metal nail, causing it to heat up due to resistance until it reaches its melting point. This process demonstrates principles of electricity, resistance, and thermodynamics, showcasing how electrical energy can be converted into thermal energy to change the state of a material. Safety precautions are essential due to the risks of burns and electrical hazards.
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greypilgrim
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Hi.
I melted a nail using a transformer with 500 windings on the primary and 5 on the secondary and 220 V input voltage, but I can't make the numbers work out. I measured the output voltage to be around 2 V, which makes sense.

Trying to measure the resistance of the nail directly with a multimeter yields around 6 Ohms, which appears be way to high. With a different power supply I can get 10 A across the nail at around 1 V, which leads to 0.1 Ohms, but this would still only lead to 20 A with the transformer, which still seems way too low to make it melt.

What's wrong here? And why is the resistance measured with the multimeter so far off?
 
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greypilgrim said:
What's wrong here? And why is the resistance measured with the multimeter so far off?
Was the multimeter calibrated? Did it have lead resistance and contact resistance? Measure it by shorting the test probes, and check the zero calibration.

What is the length and diameter of the iron? nail ?
What is the length and diameter of the copper? wire, used for the secondary winding ?
 
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The diameter is 4 mm and the distance between the contacts of the secondary is 5.4 cm. Using the resisitivity of iron, I get ##4\cdot 10^{-4}\enspace\Omega## , which seems about right.
I also found a different isolation transformer with an input ammeter that showed 3 A at 200 V, so the output current should be in the hundreds A, which makes much more sense.

First I just pushed the probes of the multimeter against the nail, which gave very unstable values. Then I used crocodile clips. Could it be that most of the resistance is due to the contacts? Should I maybe file down the surface of the nail?
 
  • #4
greypilgrim said:
Could it be that most of the resistance is due to the contacts?
Yes.

Most DMMs just aren't designed to resolve very low resistance. You would probably be better off using it to measure current, at a high current level, and then voltage and calculating the resistance.

Read about "4-wire ohmmeters" or "kelvin connections".
 

FAQ: Melting a nail with high currents

What is the principle behind melting a nail with high currents?

Melting a nail with high currents relies on the principle of Joule heating, where electrical energy is converted into heat energy. When a high current passes through the nail, the electrical resistance of the metal causes it to heat up. If the current is sufficiently high, the temperature can rise to the melting point of the metal, causing the nail to melt.

What type of power supply is needed to melt a nail?

A power supply capable of delivering high currents is required to melt a nail. Typically, a low-voltage, high-current power supply such as a car battery, a welder, or a specialized high-current DC power supply is used. The exact specifications depend on the material and size of the nail, but currents in the range of several tens to hundreds of amperes may be necessary.

Is it safe to melt a nail with high currents at home?

Melting a nail with high currents can be dangerous and is not recommended for home experimentation without proper safety precautions and experience. Risks include electrical shock, burns, fire hazards, and the release of toxic fumes. It is crucial to use appropriate protective equipment, work in a well-ventilated area, and follow safety guidelines strictly.

What materials are nails typically made of, and how do they affect the melting process?

Nails are commonly made from materials such as steel (an alloy of iron), stainless steel, copper, or aluminum. The melting point of these materials varies, with steel melting around 1370-1510°C (2500-2750°F), stainless steel around 1400-1450°C (2550-2650°F), copper at 1085°C (1985°F), and aluminum at 660°C (1220°F). The specific material of the nail will determine the amount of current and heat required to melt it.

What are the potential applications of melting a nail with high currents?

While melting a nail with high currents is often a demonstration of electrical principles and material properties, it has practical applications in fields such as welding, metalworking, and electrical engineering. Understanding the effects of high currents on materials can help in designing and optimizing processes that involve heating and melting metals, such as in the manufacturing of electronic components or the repair of metal structures.

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