Answer :
If a source of 45 volts is connected between the ends of something ...
OK, let's call it a 'wire' ... and a current of 1.5 Amperes flows through it,
then we can use one of the forms of Ohm's law to calculate the resistance
between the terminals of the source.
Resistance = (voltage) / (current)
Resistance = (45 volts) / (1.5 A) = 30 ohms
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I'm very uncomfortable calling this "a wire". In order to have a light-duty
household extension cord with a resistance of 30 ohms, the cord would
need to be almost 9,500 feet (1.789 mile) long !
What you have there is a 30-ohm resistor of some kind. If it's a wire,
it almost certainly must be a kind of wire that's manufactured to have
high resistance.
Look at this: The power dissipated by your wire is
(voltage) times (current) = (45 x 1.5) = 67.5 watts !
That's a lot of electrical power, and it comes out of the wire in the form
of heat. A wire intentionally designed to dissipate that much power is
used for very specific purposes. For example: Take this wire and wind
it around and around a pencil, so that it takes the shape of a spring, then
stretch it out to maybe 6 inches long. Then do the same thing with another
6 or 8 or 10 similar wires.
Hang them all up side by side, with half of the wires on one side and half
on the other side, maybe an inch or two apart, and then connect them all
up to the voltage.
The space in between the wires gets hot. Well done ! You have invented
the bread toaster !
