What Effect Does Goole's Entrance Have on Act 1 and How Is It Conveyed to the Audience?

English HW: ‘What effect does Goole’s entrance have on Act I and how is it conveyed to the audience?’ – (30 Minute Essay)
Goole’s abrupt, unexpected entrance on Act I has the effect of creating a suspenseful and eventually apprehensive atmosphere. This is conveyed in a number of ways; through the contrast between the Birling’s mood prior to the Inspector’s entrance, and then following his entrance, the stage directions and, primarily, the Inspector’s mannerisms and speech.
  Before the Inspector arrives, the Birling family, along with the prosperous Gerald Croft, are dining at dinner; celebrating the intended marriage of Sheila Birling to her fiancé, Gerald Croft. The event is evidently joyous, with Mr Birling explaining: ‘It’s one of the happiest nights of my life.’ He continues, ‘…we may look forward to the time when Crofts and Birlings are no longer competing but are working together – for lower costs and higher prices.’ The latter quote shows how, aside from the obvious happiness of having one’s eldest child married, Mr Birling also finds pleasure in seeing the intended marriage as a business opportunity – the union between the Birlings and Crofts companies, respectively. Evidently, before the Inspector’s arrival, things are happy and in equilibrium.
  Even before the Inspector arrives, however, a suspenseful atmosphere is created. Just before Goole’s arrival, in the company of Eric and Gerald, Mr Birling reveals his business-oriented and conservative philosophy of life in an extensive speech: ‘But this is the point. I don’t want to lecture you two young fellows again…a man has to make his own way – has look after himself…’ However, Birling’s speech is interrupted by ‘the sharp ring of a front door bell.’ The use of the word ‘sharp’ emphasises the startling effect of the doorbell, cutting off Mr Birling’s speech, implying that the Inspector’s coming presence is the only thing that can silence Mr Birling.
  The doorbell, ominous of the Inspector,...