# very basic questions

Discussion in 'General Electronics Chat' started by nuevallorker, Jan 4, 2012.

1. ### nuevallorker Thread Starter New Member

Jan 4, 2012
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Hello,

I've always been a tinkerer my whole life, and I have a generally well rounded set of skills in terms of fixing things, taking them apart etc. I've always lived in small apartments and grew up in one so I never had the space to devote to doing anything properly... until now. I've built myself a little workshop in a walk-in closet in my apartment and I can finally do some proper tinkering. So, now in my 30's, i'd like to really start getting into electronics, circuitry etc.. but i'm starting basically from 0.

The internet is so full of information that its overwhelming and i'm finding it causes anxiety in terms of trying to figure out how to learn. So, as i've done with almost everything else i've learned, i figured the best way to start is by
doing. What i usually find myself doing is playing around with things i've taken apart, messing with batteries and power sources and seeing what works and what doesnt. So i've written down the most frequent questions I run into and hopefully by getting the answers i can start to understand the bigger picture. So here goes:

1. if the dc converter on a device is 9v 1amp, could you also use a 4.5v 2amp supply?
2. I have a set of speakers which take 4 AA batteries or 6V but the DC charger is 9V, how come the two voltages work? why wouldnt the 9V fry the circuit board?
3. Whats the difference between smaller / larger batteries with the same voltage? for example, lets say a 12v car battery and a smaller 12v battery. More / Less amps? (excluding obviously having longer capacity)
4. What determines how much any given device can handle in terms of charge? for instance, why is it that some devices can work with less voltage or more voltage? how do i know whether a higher voltage / higher amp charge will ruin my device?

2. ### tracecom AAC Fanatic!

Apr 16, 2010
3,879
1,396
1. Probably not, but it depends on the exact circuit being powered. See answer number 2.
2. Because some circuits (amplifiers for example) operate on a range of voltage.
3. Batteries are rated in ampere hours, i.e., how long a given battery will provide a given current. Larger batteries of the same voltage usually have higher ampere hour ratings.
4. Same answer as number 3. In order to specifically determine the charge rate for a battery, you must know the type of battery, the voltage, the ampere hour rating. From that, you can figure the charging voltage and current.

See the AAC tutorials on this web site; they are quite good.

3. ### crutschow Expert

Mar 14, 2008
13,505
3,376
1. In general, No.

2. There apparently is a regulator on the circuit board to drop the 9V to the required voltage.

3. A larger battery of the same voltage and type will generally have a larger energy capacity and be able to deliver higher currents without overheating.

4. A device is normally rated for a given voltage at a given current.
You never want to exceed that voltage by any significant value.
How low a voltage it will work depends upon the device. Typically the voltage range is ±5% or ±10% of its rating.

The device will take the amount of current it requires independent of the current rating of the supply. The supply just has to have a current rating higher than the device requires.

nuevallorker likes this.

Apr 30, 2011
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Many of your questions go to the physics behind electronics and the chemistry of batteries. Much of this is covered to some degree in the first year of a formal electronics education course. The AAC ebook is one resource and there are others such as the NEETS program online. A local college electronics program might also be a good option.

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5. ### nuevallorker Thread Starter New Member

Jan 4, 2012
3
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Thanks.

Following up on the battery question.. so amps has nothing to do with it? Why couldn't I for instance, start my car or my scooter by putting together 8 AA batteries?

Apr 30, 2011
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Because a car requires hundreds of Amps to crank the engine and the little AAs are only capable of delivering 2 at best. You can start a car with small batteries but you'll need 1000 or more of them.

7. ### nuevallorker Thread Starter New Member

Jan 4, 2012
3
0
Right ok got it. So amps is part of the equation. I get confused when you say "current" however because from my little knowledge, current takes into account voltage and resistance but says nothing about amps.

Dec 26, 2010
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Note that though some equipment uses a charger/adaptor of a higher voltage than its battery, it is not always safe to do so.

A battery eliminator for something like a small radio will often supply as nearly as possible the normal battery voltage.

Some equipment, particularly bigger items like for instance a guitar practice amplifier may take a larger voltage from a mains adaptor to allow better performance. The circuits used have to be designed to cope with the range of voltages safely.

Dec 26, 2010
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Current is measured in amps. See this reference:http://en.wikipedia.org/wiki/Ampere

Last edited: Jan 4, 2012

Dec 26, 2010
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Electric potential is measured in units of volts, and is popularly termed voltage.

Electric current is measured in units of amperes (amps) and is sometimes termed amperage.

Electrical resistance is measured in units of ohms, and is rarely termed ohmage - a term that some people object to.

These are separate though related quantities. You would be well advised to read up about electricity to clear up any confusion about them.

Dec 26, 2010
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On reflection, perhaps my comments about current, amps, and electrical units in general could have been made more tactfully.

The intention was not to discourage further enquiry, quite the opposite in fact, but I was rather taken aback by your comment that you believed current and amperage were unrelated. This is not so, as can easily be seen from a textbook on electricity, or perhaps a search on the internet.

It really would be worth getting a better idea of what these quantities mean. Some people find a comparison with hydraulics or plumbing helpful. Here electric current, measured in amps, is represented by fluid flow, and electric potential, measured in volts, is represented by pressure. Such analogies may have their place when first trying to grasp these ideas, but in the end it is better to look at their real definitions.

Electric current (or amperage)is probably the easiest to start with. This represents the rate of flow of charge*, ultimately how many electrons pass a given point in the circuit in a unit of time. http://en.wikipedia.org/wiki/Electric_current *http://en.wikipedia.org/wiki/Electric_charge

Voltage (more strictly, electric potential (difference)) is a slightly harder concept to get hold of. The voltage difference between two points in a circuit tells us how much energy is represented by a unit of charge moving between them. Thus current multiplied by voltage equals power. Both voltage and current are therefore required to get anything useful done, like cranking a car engine over for instance. http://en.wikipedia.org/wiki/Voltage

Electrical resistance is a property of many conductors, in which the current flowing through them increases directly in proportion to the voltage applied across them. This idea will not be really meaningful until corrent and voltage are understood. The unit of resistance is the ohm (symbol, Ω ), and the relationship between current and voltage in a resistor is described in Ohm's Law. http://en.wikipedia.org/wiki/Electrical_resistance http://en.wikipedia.org/wiki/Ohm's_Law