Answer:
Explanation:
A chemical change.
Usually those are irreversible. Or they may be reversible, but the form they take may leave your object not the same as they started out.
A physical change might be just as deadly. If the object melted like a chocolate Easter Bunny then the object would be irreversible as well. Take a better example.
Suppose you are talking about a Gold Coin. If you heated it so it melted, the gold would retain its value, but the fact that it is a coin and valuable as such, means that it has lost that part of its value.
I really don't know. My instincts tell me that the chemical change is more dangerous, but I can't rule out the other choice..
Answer:
Since it us the resistance that causes the power output, it might be intuitive to think that more resistance produces more power but as P=I^2 * R one actually needs high current and low resistqnce. That means 75 W has lower resistance and higher current.
Now you may think that making the resistance very low, one gets the most power. Not so, as the circuit has wires, power source etc. All the have their resistance. In theory one gets the maximum power over a resistor when the resistor is half of the total resistance of the circuit. This in practice would be inefficient as one would lose half of the total power elsewhere. In practice circuits have fuses that limit the current and one gets the maximum power at the current the fuse is rated to. So if there is 20 A fuse, the maximum power is 2400 W and the corresponding resistance 6 ohm.
