Why birds don’t get electric shock while they’re sitting on transmission lines? ?

The upper layer is made of a non conducting material that prevents the current to go through it. So it only flows inside. That's why the birds don't get electric shock. Though if they stand near the pole where all the wires get connected they may get shock.

Explanation:

it provides an alternative energy pathway for the reaction to proceed.

a catalyst is a substance that speeds up the rate of a chemical reaction but is not consumed during the course of the reaction.

catalysts increase the rate of reaction without being used up. they do this by lowering the activation energy needed. with a catalyst, more collisions result in a reaction, so the rate of reaction increases. different reactions need different catalysts.

a catalyst works by providing an alternative reaction pathway to the reaction product. the rate of the reaction is increased as this alternative route has a lower activation energy than the reaction route not mediated by the catalyst.