Question

REALLY NEED HELP PLEASEE!!!

Answer 1

Third (current carrying) rail of subway track is made of steel and has a cross-sectional area of about 11cm^2.
What is the resistance of 4km of this track

Answer 2

The resistivity of steel is 1 x 10^-7

Answer 3

its a direct question apply resistance formula.. before that do conversion of the quantities to same unit

Answer 4

i mean do i just multiple them?

Answer 5

I just started the class and i havent gotten all the formula's down

Answer 6

resistance = resistivityx(length/cross sectional area)
note that the area is in cm^2 and length in km

Answer 7

so 4000 would be for 4km

Answer 8

yes

Answer 9

and 0.0011 would be for the cm

Answer 10

no

Answer 11

sorry 1m = 100cm
1km = 1000m

Answer 12

So i would do

1 x 10^-7 TIMES .00011 DIVIDED by 4000?

Answer 13

you shoul check the unit of resistivity.. if its in SI then you have to convert the distances in to metres

Answer 14

its in ohms meters

Answer 15

ok then convert both the distances to meters..then apply formula

Answer 16

Okay and one more question

Answer 17

If there were two straight wires each carrying current

what would the dirction of the magnetic field at point R cause by the two current carrying wires