If the writer's account of events was verified by an eyewitnesses
Its a primary source as it comes off a tree - cant get more primary than that
Primary is the source you can depend the most upon because it is the first source therefor it is used more often.
A secondary source is more helpful when you are looking for analysis, interpretation, or synthesis of information already presented in primary sources. It can provide additional context, perspective, or critical assessment of the primary sources.
If the primary source is AC, then that's the job of a transformer. If the primary source is DC, then doing that requires considerably more complex electronics.
Interviews are primary sources 'cause the interviewers are getting the information from the source.
When you are not an expert in the field being studied in the experiment
Usually you will need 'the broad picture' and a primary source won't give you that.Making sense of primary sources is often extremely difficult without expert knowledge of the subject.Primary sources are easily misunderstood.
They summarize conclusions about primary sources.
One can find more information about primary care trusts from: NHS Choices, The Age UK, Primary Care trust Directory, Red Bridge, Binleys, Guardian, Saga.
Research into the source. Everyone has an axe to grind, an angle and a purpose. Each of these will colour the viewpoint as no one is truly objective. Once you understand what the motives of a source are you can examine it more clearly. For instance, a medieval writer trying to get noticed and seek advancement from the king will want to flatter and gloss over the negative and exaggerate the positive. They may want to make the king seem more intelligent, more courageous in battle, or more fearsome so any passages written about a battle would need to be verified to be trustworthy. If another, independent, source agrees with the sequence of events or sentiments expressed then it could be that the version is more trustworthy, as long as that second source isn't using the first as its basis or has the same set of motivations. For instance, we can know that the Battle of Hastings was fought at the place now called Battle as all sources, English and Norman agree. There also has been archaelogical evidence discovered to back it up. That will allow you to trust a the sources more. But where a source is the only one to attest something, then only examination of it can help.
written or caused by someone who did not experience an event. from APEX
It would be a primary sourcebecause it is word for word as it was written. In a similar more obscure way, letters written by Adams to Jefferson are primary sources.