short circuit 問題!!!

1) The following is a situation when S is closed:
Compare with the resistant of L1 and S, S has no resistance.(By assuming that wire has no resistance.
As a result, S has infinitively large current, while L1 has very low current (no current).
For no current passes through L1 due to the zero-resistance wire, we say that L1 is short-circuited.
至於第2同第3條呢 我唔係太肯定
不過就等我估下啦xd
希望有人識答ge話咁我都可以知道
2) There should have no current passes through PQ because the equivalent resistance across L1 and L2, L3 and L4 are the same. So, current is not necessary to be drawn from either P to Q or Q to P.
3) There should be a current passes through PQ because the equivalent resistance across L1 and L2, L3 and L4L5 are different. Current pass through L1 and L2 are the same, but the pass through L3 is larger than L4L5. So, current is necessary to be drawn from Q to P.

1.有current流過L1,唔算係short circuit
這是open circuit
把s close ,就係short circuit

2.有,你可以把circuit畫唔同的樣,就睇到

3.同(2.)