A piece of Nichrome wire has a radius of 6.5 104 m. It is used in a laboratory to make a heater that uses 4.00 102 W of power when connected to a voltage source of 120 V. Ignoring the effect of temperature on resistance, estimate the necessary length of wire.

Explanation:

Given data

Power P=4.00×10²W

Radius r=6.5×10⁴m

Voltage V=120V

To find

Length of wire L

Solution

We know that resistance of wire can be obtained from

We also know that R=pL/A solving the length noting that A=πr²

and using p=100×10⁻⁸Ω.m we find that

So

18 group.

The group 18 elements of periodic table never forms a ionic bond. Only this group is the exception where all the elements present in the group does not form any ionic bond. There are other elements also that do not form ionic bonds but not complete group. The noble atoms have complete outer shell so they can neither lose or gain any electron which form the group 18.