Hi Susan, I had the same question as the original poster, and even after reading your reply I’m still confused.
I understand that in circuit B, all the current will flow through the shunt because there’s no resistance there. But why isn’t the same thing true for circuit A? I understand that the switch is open in circuit A, but wouldn’t the current still want to flow there because there’s no resistance? What difference does it make if the switch is open if there’s no resistance either way?
