In SR latch when apply a pulse to reset latch how the Q is changed?
The truth table of a NOR gate tells you that the output will only be 1, if both inputs are 0. As soon as one input gets to logic 1, the output switches to a logic 0.
When R is set to 1, the condition of both inputs being zero is no longer fulfilled -&gt; The output goes immediately low to 0.
At this time the lower NOR gate still has to wait for the logic 0 to appear at its upper input - until than it will stay low. But as soon as the higher input sees the 0 from Q, the gate has two low 0 as input and will switch the output to 1.