The differences between the generations are very clear. Even at the very beginning of the play it is shown:
Sheila: “You’re squiffy”
Mrs Birling: “What an expression, Sheila!”
Here it is showing that Mrs Birling does not really understand how the younger people talk. It means that the audience can see at once that there is a difference between the younger people and the older people.
The difference between Sheila and Birling are not shown until later on in the play.
The first signs of the generation gap is in Act 2, where Sheila says:
“Don’t interfere, please, Father. Gerald knows what I mean, and you apparently don’t”
This is the first real sign of tension. It makes the audience more sympathetic towards Sheila, because her father does not understand what has happened between her and Gerald. This is because the older generation do not understand how the younger generation work out their problems.
Sheila has already explained how she and Gerald should sort the problems out, but her father still thinks that he can fix the situation.
The main difference between Sheila and Birling is shown after the Inspector leaves. It is whether the Inspector was really a police inspector, and whether it matters if he was or not:
“But it doesn’t make any real difference, y’know”
Sheila is sympathetic towards Eva, whereas Birling is more concerned about his public image. The audience are sympathetic towards Eva, and so it makes them feel resentful towards Birling.
This shows a clear division between the two generations, and how they view the situation. This has a dramatic impact on the audience. They will not have viewed Birling in this way until he seems unsympathetic towards what happened to the girl. They feel betrayed by his character.
Birling accuses Sheila and Eric of telling the Inspector too much, however, he defends his wife:
“No, not you, my dear. But these two”
Birling wants to clear his conscious and blame someone else, whereas Sheila wants to share the blame, and accept her responsibility. The audience feel that Birling has a weak character because he has to side with his wife, and blame his children. They feel that no one should blame their children in this way, and so they are unsympathetic towards Birling.