You have been sending us your questions about how the election works. Here's a selection of them and our answers.
What would happen if the Queen refused to dissolve Parliament when asked?
Kate Sanders, Chichester
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It would trigger a huge constitutional crisis about the powers of the monarch against the wishes of the elected prime minister. But, as Tony Blair said, the Queen has "graciously consented" to wind up Parliament.
What happens if no one party gets an overall majority of seats?
Tom Nicholas, London
Then there is a hung parliament. The main parties have to try to form a coalition with one or more of the minor parties. February 1974 was the last time an election failed to produce a majority. The Tories won four fewer seats than Labour. After four days of trying in vain to win support from the Liberals, leader Edward Heath had to resign as prime minister.
I am under the impression that once Parliament has been dissolved Tony Blair is no longer prime minister. Who is in charge during the period between the dissolution of Parliament and the election of a new government?
Chris, Farnham, UK.
There are no MPs once Parliament is dissolved but ministers, including Tony Blair, do continue their government jobs - and civil servants continue to help them run the country.
How is a swing calculated? Labour was 9% ahead at the last election and is 3% ahead in the polls now. Is that a 6% swing? Or is it more complicated?
David Tittle, Coventry, England
It is a bit more tricky. Swing is how you measure the switch of voters from one party to another. To calculate it, you add together one party's vote to the fall of the other, and then divided the total by two. So if party one's vote rises by 4% and party two's vote falls 5%, the swing is 4.5%.
Why has the number of constituencies in Scotland changed?
Nigel Ashton, Southport, England
Scotland will have 13 fewer seats at this election. Until now, the numbers of voters in Scottish constituencies have been significantly smaller than those in England. Part of the devolution settlement was that they should be brought more into line with those south of the border. The next general election will see major boundary changes in England and Wales.
I'm away at university but my voting card will be sent to my home in Wolverhampton. Can I vote here in Leeds?
Tom Grundy, Leeds, Yorkshire
You will have to be on the electoral roll in your university town - you can be registered both there and at home but are only allowed to vote once. It is now too late to register but it is worth checking that your college principal has not registered you already. To vote at home, you could arrange a postal or proxy vote by contacting the council there.
Who are the people who administer polling stations and take part in the count? Are they civil servants, political party officials or volunteers?
David Bradwell, London, UK
Polling stations are generally staffed by council staff or sometimes by volunteers, but not political party officials. Bank tellers are often hired for the actual counts.
Why is the election being called after only four years instead of five?
E Thompson, London, England
It is up to the prime minister to choose to hold the election any time up to five years after the last poll. He has consistently chosen four year terms of government. The argument is that if things are going OK it is better not to risk waiting until the 5th year. James Callaghan did wait in October 1978 and had to face the polls after the Winter of Discontent.