In physics, Ohm's law says that current through a wire, I, is directly proportional to voltage, V, and inversely proportional to resistance, R: I=V/R It's also true that resistance is directly proportional to the length of the wire. We have a piece of wire. We pass 50 volts through this wire and measure 200 milliamps of current. If I cut the wire in half and pass 250 volts through it, how many milliamps of current will I measure?
First of all ...you do not 'pass 50 volts through a wire' you apply 50v across a wire and pass a current through the wire.....
I = V/R
.2 = 50/R R of the wire is 250 ohms
1/2 of the wire would be 125 ohms
Now apply 250 v across the wire
I = V/R
I = 250/125 = 2 amps (2000 miliamps)