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# aops problem - cphill please help! this problem is so hard :((

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In physics, Ohm's law says that current through a wire, $$I$$, is directly proportional to voltage, $$V$$, and inversely proportional to resistance, $$R$$ :

$$I=\frac{V}{R}$$

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?

Mar 15, 2020

#1
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If you put 250 volts ACROSS the wire (you don't put voltage THROUGH a wire) the curent woud increase through the wire

250/50=  by 5 times       5 x 200 ma = 1 amp

EDIT:::::

BUT   you cut the wire in half....this cuts the resistance in HALF

cutting the resistance in half will DOUBLE the current through the wire

1 amp x 2 = 2 amps   = 2000 millimps

Mar 15, 2020
edited by ElectricPavlov  Mar 15, 2020
#2
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i just checked and its wrong

Mar 15, 2020
#3
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It is not incorrect      1 amp = 1000 milliamps  ,   silly !

ElectricPavlov  Mar 15, 2020
edited by ElectricPavlov  Mar 15, 2020
#5
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Actually, it is wrong, EP.

The voltage increased five (5) times, and because the wire is now half as long, the resistance is now 125 ohms

or (1/2 * 250) ohms. This means (2) amps or (2000) miliamps of current now pass through the wire.

GA

GingerAle  Mar 15, 2020
edited by GingerAle  Mar 16, 2020
#6
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Thanx GA....missed the 1/2 as long part  !!!!!

I apologize !!!!!

the voltage increased 5 times   and the resistance is cut in half    so the current will increase   5 x 2 times

10 x 200 = 2000 mamps

D'Oh !

ElectricPavlov  Mar 15, 2020
edited by ElectricPavlov  Mar 15, 2020
#4
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i know! that's what i entered lol and it was marked wrong

Mar 15, 2020