Electrostatics
Electromagnetics
Electricity & Magnetism
© The scientific sentence. 2010
| Ammeters & Voltmeters
The main feature of an element in an electric circuit such as a
resistor, capacitor or inductor is the relationship
between the potential difference V across the element
and the current I in the element. The simple relationship
of un element is Ohm's law for a resistor of resistance R:
V = RI. The quatities V and I can be measured
by instruments. Current is measured with an Ammeter, and
potential difference with a Voltmeter. The ammeter is
a device that measures currents in Amperes (A), the
voltmeter a device that measures voltages in Volts (V).
1. Ammeters
To measure the current in a circuit element, an ammeter must be
placed in series with the element. An ammeter measures the
current in itself. The current in the ammeter and in the element are
the same.
The galvanometer is an ammeter with high sensitivity.
2. Voltmeters
To measure the potential difference across an element in a
circuit, a voltmeter must be placed in parallel with this
element. A voltmeter measures the potential difference across itself. The potential difference across the element and across in the voltmeter are
the same.
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