00:01
Hello student, here the resistance of the copper wire at 30 degree centigrade is 25 ohm.
00:14
Let's consider the length of the copper wire, length is l at 30 degree centigrade.
00:26
So, length of the wire 75 degree centigrade will be l plus l into alpha delta t, where alpha is the temperature coefficient and delta t is the temperature difference.
00:44
Now, substituting the value of alpha and delta t, we have l dash equals to l into 1 plus 0 .004, which is the temperature coefficient into 45, difference between the temperature.
01:03
So, this is equals to, so we can write l dash by l equals to 1 .18.
01:21
Now, volume of the copper wire remains the same.
01:27
So, we can write a times l equals to a dash l dash.
01:35
So, from this we can write a by a dash equals to l dash by l, which is equals to 1 .18...