(A) We can solve the problem by using Ohm's law, which states:
![V=IR](https://tex.z-dn.net/?f=V%3DIR)
where
V is the potential difference across the electrical device
I is the current through the device
R is its resistance
For the heater coil in the problem, we know
![V=220 V](https://tex.z-dn.net/?f=V%3D220%20V)
and
![R=220 \Omega](https://tex.z-dn.net/?f=R%3D220%20%5COmega)
, therefore we can rearrange Ohm's law to find the current through the device:
![I= \frac{V}{R}= \frac{220 V}{220 \Omega}=1 A](https://tex.z-dn.net/?f=I%3D%20%5Cfrac%7BV%7D%7BR%7D%3D%20%5Cfrac%7B220%20V%7D%7B220%20%5COmega%7D%3D1%20A%20%20)
(B) The resistance of a conductive wire depends on three factors. In fact, it is given by:
![R= \rho \frac{L}{A}](https://tex.z-dn.net/?f=R%3D%20%5Crho%20%5Cfrac%7BL%7D%7BA%7D%20)
where
![\rho](https://tex.z-dn.net/?f=%5Crho)
is the resistivity of the material of the wire
L is the length of the wire
A is the cross-sectional area of the wire
Basically, we see that the longer the wire, the larger its resistance; and the larger the section of the wire, the smaller its resistance.
So the best conductor for electricity is silver.
However because silver is so expensive we use copper which is the next best conductor