You got some good answers, but you can take things a bit further I imagine... Let's elaborate some for fun.
-What are two different cables that transmit audio and video at the same time through one cable? I have HDMI as one but i dont know the other.
Coax? Check, but what about Firewire? For DV cameras and some DVD recorders, this can be used as well. Realistically, only one of these I believe puts the audio on the same wire as the video and that is coaxial. HDMI consists of something like 21 separate wires inside a single jacket... If I took RGBHV/Componet/S-Video/Composite, and bundled it with 5 stereo pairs, then ran it through snake skin - it may appear as 'one' cable, but it doesn't change that it is truly a bunch of different cables. Unlike coax which really is just a single cable carrying both audio and video.
-List three different types of video cables capable of transmitting a high definition signal.
HDMI, Component, DVI, RGB/VGA. It's important to know that the X-Box 360 only allows DVD upconversion over a VGA connection and not over component video, it also lacks a HDMI/DVI output. Good info for your customers - first ASK what they are trying to connect, then give them the right solution.
-list two different types of digital audio cables. I think fiber optical is one but i dont know the other.
The two types are coaxial and fiber. Toslink, or Toshiba Link is a set of protocols defining a digital transmission standard, but is most often associated with fiber cables. S/PDIF is the Sony / Philips Digital InterFace and is most often associated with coaxial digital audio. The two are fairly easily converted between each other if someone runs out of inputs on their receiver.
-what is the purpose of hdmi?
Definitely to simplify installation.
HDMI also delivers digital video and audio which means that it is less susceptible to interference and noise that regular analog video cables, like component video, can pick up. Lots of additional protocols are included within HDMI, but those two items are the biggest advantages for HDMI.
Biggest disadvantages for HDMI? Gotta be the distance limitation, though this is fading, and the inability to easily split/matrix HDMI to multiple locations.
-what type of cable is required to connect powered speakers to a computer? Would it be a 3.5mm mini cable?
Pretty much - remember 3.5mm = 1/8". Make sure that you are selling them a 1/8" STEREO cable - male to male. 1/8" stereo mini is often the term used.
-What are some essential accessories needed for a home theater system? so far i have speaker stands and speaker cables. i need 3 more
Speaker cabling to be considered different than interconnects which are also required, definitely a decent surge supressor/power conditioner, a decent equipment rack to hold everything would be nice, and definitely don't forget that universal remote. Heck, upsell them to a front projection setup and really start to accessorize!
-a customer wants to purchase a dvd player but their tv only has coaxial input. what type of accessory would you sell the customer? i know what to get but i dont know the name of it.
Properly stated before - RF Modulators will do the trick. The newer ones include inputs for cable TV and a local source. When it detects a signal from the DVD player it will automatically switch from the cable input source to the DVD input source to maintain the highest quality picture possible.
-a customer walks into the store and decides to buy a flat panel tv for their home. what are the essential accessories needed for this setup. i have wall mounts and cables and i need two more.
Similar to buying a home theater, you want surge supression, a decent remote... at a retail store? Don't ever forget the 'extended warranty'! You also want to make sure they have a DVD player and HD DSS receiver to deliver the best in content for their display.
-Name The Two Digital Surround for formats used on today's audio receivers?
This is pretty well covered in detail above - DD and DTS with DTS generally being considered better...
-what is the main difference between these two formats?
...because of the higher bitrate DTS offers.
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I'll skip the car questions as they were pretty well answered to the best of my abilities already.
Questions that they didn't ask that you should really know the answers for are as follows:
1. What are the 5 different main television technologies on current digital displays?
2. What is the difference between them?
3. When should you use them?
4. What is the proper screen size for a 10'x12' room?
5. What is the difference between HD DVD and Blu-ray?
6. What do the power specifications on an A/V receiver mean?
7. What are ohms and why do they matter?
8. What are the different types of speakers?
9. How do you wire for a 7.1 audio setup?
10. Where is the proper placement for speakers in a 7.1 setup?
11. What does 5.1 and 7.1 even mean?
12. Why won't someone hear sound from their surround channels when watching TV, or listening to a CD? (most of the time)
13. Name 3 different ways to hide wiring.
