Question

A 20-cm long and 1.0-mm diameter thick copper wire (resistivity 1.7 × 10-8 Ωm) is connected across a 3-V battery. The current through the wire is
1-7 A.
2-125 A.
3-693 mA.
4-693 A.
5-789 A.

Answer 1

@experimentx @jhonyy9 @ishaan94

who know the answer gyus but please quickly i have 15 min only to solve these one :( :\

Answer 2

@siddharth18 do u can solve it :)

Answer 3

from ohm's we know that v=ir
now we have v=3V
r=(resistivity*length)/area of cross section of the wire
i(current)=v/r
radius of the wire=0.5mm
now u have all the values,just substitute them in the formula for i and calculate

Answer 4

area of cross section is given by pi*r^2

Answer 5

make sure u use SI units

Answer 6

are u sure from how to get the area ?

Answer 7

yes i m

Answer 8

but i get the answer 0.01298 can u check and tell me what u get please ?

Answer 9

but i get the answer 0.01298 can u @siddharth18 check and tell me what u get please ?

Answer 10

my answer is 789amperes

Answer 11

yes yes it was mistake by me i check it and i get 789 :P
thanx very much for helping me do u need any thing in physics :P or math

Answer 12

do u mean to say doubts?

Answer 13

here you are..

Resistance = [resistivity] * [length] / [ cross sectional area]

= [1.7*10^-8] * [ 0.2] / [ pi * (10^-3)^2 /4 ]
= 4.33*10^-3 ohm

Now, current = 3 / resistance = 3/ ( 4.33*10^-3) = 693 Amperes

@Siddharth18 did I do sth wrong mate?

Answer 14

@blacktigger how did you guys get 789 A?

Answer 15

my resistance is coming out to be3.98*10^-3ohms

Answer 16

when i checked my answer on the web site i found that 693 A is the right answer good
job mate @bhaweshwebmaster

Answer 17

@siddharth18 but u did agood joob also ty

Answer 18

no big deal man,it was just the calculation.
the approach is what matters more