Amy Winehouse

Locating switched live wire?

I am trying to find the switched wire in a ceiling rose (I didn’t take the original fitting off) and I believe it is at the end of a loop as there is only 2 white cables coming through the ceiling. From what I have been researching so far I am understanding that it will be a black wire which will need to be taped with a bit of red insulating tape (when found), I have a B&Q Pocket Digital multimeter but I’m not entirely sure how to use it? Any suggestions? I think it’s the continuity option that I’m looking for or low Omz? Not entirely sure, I will make sure the mains is off fully before doing anything. After I have found the correct wire does it go in to the terminals with the brown live wire from the light flex? I have done some electric stuff around the house so far, changing light switches and socket and earthing metal socket to a metal back box so I don’t think I’m out of my depth here but want to be sure on how it is done correctly.
I live in the UK so I need to make sure I am following the correct regulations

voltmeter internal resistance?

300V supply two resistors in series 5M ohms and 10 M ohms
A voltmeter with an internal resistance of 10 M ohms is connected in parallel with the 10 M ohms resistor what will the voltage indicate on the voltmeter? Please can you explain

how to know what an ammeter will say in a circuit in physics?

HELP!!!!!!!!!!!!!
I have got a physics test this week and i can’t understand this rule. How do you calculate what it will say? the questions we are going to have will give a diagram with and ammeter on it and it will ask for the amps on the ammeter

any help will be appreciated
thanks
x

Current and Voltage of a Simple Curcuit?

Consider a simple circuit of a battery and two resistors connected in series. discuss the proper technique for measuring current, voltage (of each resistor), and the equiv. resistance with a multimeter.

Can I safely assume 100% that it\’s my amplifier\’s problem?

The basics of my problem: I receive a new amplifier from ebay after my old amplifier broke on the road. The new amplifier, once hooked up correctly can’t power my subwoofer at all. I begin to wonder if perhaps my old amp actually worked after all and it was something else that was the problem. After enormous amounts of trial and error I’m still unsure if it’s safe to assume 100% that the new amplifier is the problem. I definitely don’t want to go through an ebay return if I don’t have to.

I hooked it up to a small 6 1/2 inch door speaker and was surprised to get a very small output from it. It was low pitched and very soft even though the amplifier is 400 watts rms at 4 ohms (which btw both my subwoofer enclosure and door speaker are @ 4ohms) and the amplifier was at maximum sensitivity, which should have resulted in one very fried door speaker, but it didn’t. I also tried various other things which I cover in the details below:

Is there anything remaining that hasn’t been tested one way or another conclusively?

Subwoofers (tested on a door speaker which is known to work with head unit outputs of only 10 watts or so and only got tiny sounds from it)

RCA cables (tested using a portable DVD player and separate RCA cables, same problem with the door speaker and the subwoofer)

Head unit
(tested using another head unit and same problem, also this head unit was the one I was using previously and it worked with my old amp when I took it out)

Subwoofer wires (used the same wire on the door speakers and it’s a see through 10 gauge high output wire with no problem areas)

1X 60A AGC glass fuse near battery (was taken out and the wire bonded together without the fuse resulting in the same problem)

3X 40A plastic fuses on the amp (They appear to be intact, I checked each of them closely although I need a voltmeter to confirm)

1X 10A fuse on head unit (Connected with copper wire (bypassing the fuse) and tried it to be sure resulting in the same problems)

Power cable + 8 gauge from battery (sparks against the frame just like it used to — very violently)

Power cable – 8 gauge (connected to a new spot that’s 100% bare from paint and then tightened
excessively to ensure contact)

Battery (Well it starts the car fine, that should be enough)

The amplifier has enough energy from the remote and power cables to turn the power protection light to green also, so I know it’s getting at least some power and the remote cable is in all likelihood working as well.

Once again I’m at a loss. If the voltmeter picks up 12v or more between the terminals and 2v on the signal cables later today can I safely assume it’s the amplifier? Or what else can I do to be sure? It’s been driving me crazy over the last 3 or 4 days.
Yeah that’s what I was thinking. The seller is pretty convinced that the amp worked when he packed it up. It seems like it could turn into a he said she said battle which is what I don’t want.

I’ve got a friend with a system but he’s not willing to let me do anything with it _ I’ve installed mine just fine but he thinks I’ve got destructo-fingers or something. Some friend right? I got nothin else to do.
I never really thought of that, but the speaker itself is hardly moving. 400 watts should be popping the speaker like popcorn and instead it just makes the cone shake a little bit. I’d say about the level that you’d watch a movie on while trying not to wake up the person sleeping next to you.

My equipment is as follows:
rockford fosgate amp wiring kit
jvc ks-ar7501d (amplifier)
sony xplod XS-L120B5D (subwoofer enclosure)
Pioneer DEH-3100UB (headunit)

97 Mitusbishi Galant is the car for speaker sizes and whatnot

What is high current and low current?

I got the following results and I am not sure how to explain it. Does the results means as the length of nichrome wire increase the resistance increase? cuz in theory it should. Also if the ammeter said 3.1 does that means low resistance/current? Thanks.
Results:
Length of wire Average current
10 3.1A
15 2.46A
20 1.6A
25 1.4A
30 1.2A
35 1.0A
40 0.9A
45 0.8A
50 0.7A

where/how can i learn how to use cars diagnostic systems and digital multimeters?

i want to buy diagnostic system or digital multimeter, where or how could i learn how to use are there any not expensive ways how to learn it?

why barrier potential can not be measured externally with a voltmeter?

How many ohms does a multimeter read for a closed circuit, such as a good fuse or good wire?

Maytag Washer Check Switch?

Anyone know the details of why there is a check switch, in addition to a lid switch on my 1992 Maytag Washer? Seems like there’s a problem with it. If I check it with my voltmeter when the washer shuts off (during mid-cycle) there is no voltage. If I tap it with a screwdriver, the voltage returns and the cycle completes. I’m thinking of jumping it out but unsure what the extra leg/switch is for. Any guesses? Here’s the assembly and the bottom switch (labeled “check switch” in photo & what I tap): http://www.american-appliance.com/images/image_data/maywashlidswitch.jpg