Video Transcript
Which of the following quantities
does an ammeter measure? Is it (A) electric charge, (B)
potential difference, (C) electrical energy, or (D) none of these quantities?
This question is asking what
quantity is measured using an ammeter. A clue to the correct answer is in
the word “ammeter.” Measuring devices are sometimes
called meters. For example, a thermometer measures
temperature. The name thermometer tells us this
instrument is a thermo-meter. It is a thermal measurement
device.
What then would an ammeter be used
for measuring? What does am- mean here? We can consider the quantities
shown and see if A-M or am- relates to any of them. Electric charge is not sensibly
abbreviated by A-M. The unit of electric charge is the
coulomb. This unit is also not sensibly
abbreviated by A-M. Electric potential difference is
not sensibly abbreviated by A-M. The unit of potential difference is
the volt. This unit is also not sensibly
abbreviated by A-M. Electric energy is not sensibly
abbreviated by A-M. The unit of energy is the
joule. This unit is also not sensibly
abbreviated by A-M.
None of these quantities seem to be
good candidates for what an ammeter would measure. Let us consider the quantity
electric current. Electric current is not sensibly
abbreviated by A-M. However, the unit of current is the
ampere. Ampere can be sensibly abbreviated
by A-M, and in fact ammeters do measure electric current. We see then that the correct answer
is option (D). None of these quantities are what
an ammeter measures.
