Video Transcript
Which of the following devices can
be used to measure electric potential difference? Is it (A) an ammeter, (B) a
voltmeter, (C) a newtonmeter, (D) an ohmmeter, or (E) potentiometer?
This question is asking what device
can measure an electric potential difference. All the measuring devices end in
-meter. Measuring devices are sometimes
called meters. For example, a thermometer measures
temperature. The name thermometer tells us that
this instrument is a thermo-meter; it is a thermal measurement device.
It might seem that the answer is
option (E), potentiometer, as potentio- is similar to potential difference. Actually, a potentiometer can be
used to indirectly measure an electric potential difference, but not directly. A potentiometer is certainly not
the device that is typically used to measure electric potential difference.
For many devices, the part of the
name of the device that precedes -meter is the name of the unit of the quantity that
the device can measure. For example, an ammeter proceeds
-meter with AM, which stands for amperes. Amperes are the unit of electric
current. We have just seen that the answer
is not option (A) as an ammeter measures electric current rather than electric
potential difference.
Recall that the unit of electric
potential difference is the volt. This implies that a voltmeter would
be the name for a measuring device for measuring electric potential difference. In fact, that is exactly what a
voltmeter is used for. A voltmeter can directly measure an
electric potential difference, and it is the standard measuring device for doing
so.
We see then that the correct answer
is option (B). A voltmeter measures electric
potential difference.
