Video Transcript
Which of the following is the
correct unit for electric current? (A) Volt, (B) joule, (C) ampere, or
(D) watt.
Units are an important part of
every physics problem. Not only do they communicate the
exact type of quantity we are working with, but they can also include clues to help
solve the problems. If we can identify the type of unit
that the answer should have, then we can sometimes determine how to find the answer
to the problem. In this question, we want to find
the correct unit for electric current. Let’s go through each answer option
to work out which is the correct answer.
Option (A) suggests the volt. When we think of volts, we might
think of potential difference because potential difference is measured in units of
volts. Potential difference is a measure
of how much energy is needed to move a charge through a component. Hence, we cannot measure electric
current in units of volts. So option (A) is incorrect.
Option (B) suggests the joule. When we think of joules, we might
think of work and energy because the joule is a unit that measures these
quantities. Energy is the capacity to do work
or to produce heat, but this is not the same as electric current. Hence, we cannot measure the
electric current in units of joules. So option (B) is incorrect.
Option (C) suggests the ampere. When we think of amperes, we might
recall that amperes are a unit of electric current. Electric current is the flow of
electric charge around a circuit. It tells us the rate at which
charge passes a point in a circuit. If one coulomb of charge flows past
a point every second, then there is one ampere of current in the circuit. Because electric current is
measured in amperes, option (C) seems to be the best choice. But to be sure, let’s look at the
final choice.
Option (D) suggests the watt. When we think of watts, we might
recall that the watt is the unit of power. One watt is the rate at which work
is done when one ampere of current flows through an electric potential difference of
one volt. Hence, we cannot measure the
electric current using the watt. So option (D) is incorrect.
So we have ruled out all other
answer options except for option (C). Hence, option (C) is the correct
answer. The ampere is the unit of electric
current.
