Electric potential and electromotive force are alternate names for voltage. Remember that voltage is present even if no current is flowing; a battery may be a 9 volt battery even though it is not connected to anything. Thus, it is referred to as electric potential, or electromotive force.

And, as you may guess, voltage is measured with a voltmeter.

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Tags: instruments electromotive force (voltage) section6.8

A voltmeter is used to measure potential difference across two points in an electrical circuit.

The voltmeter is connected in parallel at the points that you wish to measure voltage drop between, which usually means connecting it on each side of a given load (which has resistance and thus voltage drop).

A theoretically ideal voltmeter has infinite resistance; an "ideal" voltmeter thus has no effect on a circuit if connected in parallel but in series would entirely prevent the flow of electricity.

Ammeters are connected in series to the circuit element you want to measure. (Series means that the circuit is changed to go through the ammeter rather than merely connecting it to existing points without otherwise changing the circuit)

All elements that are in series with each other have the same current.

A theoretical ideal Ammeter has no resistance and thus no voltage drop, so adding the ammeter in the circuit should not change the current the circuit.

Be careful with this question, make sure you know Voltmeter from Ammeter!!!!!

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Tags: instruments electromotive force (voltage) section6.8

An ammeter measures current flow. Unlike voltage, which is potential, current represents actual movement of energy and work done through the system. Thus, in order to measure how much of it is flowing, the current must flow through the ammeter. That means that an ammeter must be connected in series with the circuit in order to get an accurate reading and in some cases avoid blowing the fuse in the meter.

Do not connect your ammeter in series with a power source with no load or there will be nothing to limit the current flow and you will blow the fuse in your meter! An ammeter (or a multimeter with the probes connected in the amp measuring ports) ideally has no resistance and thus no load, similar to a piece of wire. Connecting it in the wrong manner is just like causing a short circuit with a piece of wire.

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Tags: instruments electrical current section6.8

Electric current is measured in amps and is measured with an ammeter. The other meters listed here are:

• Ohmmeter: used to measure resistance in ohms
• Wavemeter
• Voltmeter: used to measure voltage

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Tags: instruments electrical current section6.8

The resistance setting on a multimeter behaves as an ohmmeter to measure resistance. In general, an ohmmeter measures resistance by applying current through the resistor and measuring the resulting voltage drop.

If you connect an ohmmeter to a voltage source, the resulting external current applied by the voltage source could seriously damage the components of your ohmmeter (in this case, your multimeter in ohm mode).

As good practice, always check the multimeters setting to ensure it is in the correct mode and range for the expected measurement. If in doubt, start at the highest voltage range and lower until you get an in-range reading. Also, NEVER connect a meter in the Current mode to a voltage circuit as it will short it out and damage the meter, even if this is only blowing the protective fuse inside.

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Tags: instruments electromotive force (voltage) resistance section6.8

A multimeter is thus named because it combines several measurement tools in one device. Most common multimeters these days provide an ohmmeter, an ammeter, and a voltmeter.

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Tags: instruments electromotive force (voltage) resistance section6.8

Acid-core solder is used to strip the oxidation layers off of metal objects to create a joint. It is mostly used in applications like plumbing where a water-tight seal is needed. It is not suitable for electronics due to the corrosive effects. An easy way to remember is that acid eats away at metal and that is not good for electronics where very thin metal contacts may be used.

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A "cold" solder joint results when not all metal surfaces are properly fluxed, brought up to the needed temperature, or if the solder is disturbed during the "plastic phase" as it cools and hardens

When this happens, the surface of the solder joint will appear dull or grainy instead of bright and shiny. Inspect every solder joint to ensure that the solder flowed smoothly over all conductors being joined.

A small crack in the solder around a large conductor is an indication that it was not heated sufficiently. Remember not to "play" with the solder, just heat up the whole connection until the solder flows freely filling all gaps, then remove the soldering iron and let it cool undisturbed.

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Tags: troubleshooting electronics section6.8

Ohmmeters measure electrical resistance, so the options regarding full-scale readings and open/short circuit are out.

If a capacitor is discharged, that means that it is no longer storing electricity. When you hook up an ohmmeter across such a capacitor, the current coming out will constantly decrease. Thus, the ohmmeter will detect that and measure the resistance as increasing, as the power difference going in and out will be larger.

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An ohmmeter measures resistance, not voltage. Since resistance is basically a function of the voltage drop across a given portion of a circuit to the current applied across that same portion of the circuit (R=E/I), the ohmmeter applies a small current to the load and then measures the voltage drop across it. If the circuit is powered, not only will that affect the voltage readings that the ohmmeter will be taking but will likely be so much higher than the ohmmeter is using that it could (probably will) damage the circuitry in the ohmmeter.

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