Many television receivers are connected to an aerial using a coaxial cable. Such a cable is illustrated in the figure below.
State two functions of the copper braid.
Suggest two reasons why a coaxial cable is used, rather than a wire pair, to connect the aerial to the receiver.
A coaxial cable has an attenuation per unit length of 
. The length of the co-axial cable between an aerial and the receiver is 
. Calculate the ratio
