(a) Electricians wear rubber hand gloves while working with electricity because rubber is an insulator and it will prevent them from getting electric shock, in case of short circuit or overloading.
(b) We know that V = IR
Here, I = 6 A
R = 40 Ω
So, V = 6 x 40
V = 240 V
So 240 V is the potential difference needed to send a current of 6 A through an electrical appliance that has a resistance of 40 Ω.