Having laid the foundations for designing an electrical circuit in the previous video in this series we're now going to start crunching numbers by figuring out how to calculate design current. Why is design current so important, where do we get the values for figuring it out from and why don't we use the exact same symbols we learnt in our science lessons? Heat is both the result and the enemy of electrical installation and in this video we start to explore just how to make sure that heat doesn'