Video Transcript
Which of the following is the
correct unit for electric charge? (A) Ampere, (B) volt, (C) joule, or
(D) coulomb.
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 charge. Let’s go through each answer option
to work out which is the correct answer.
Option (A) suggests the ampere. When we think of amperes, we might
think of electricity, because amperes measure electric current. Electric current is related to
electric charge, but they are not the same thing. 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, but it doesn’t describe the charge itself. Hence, we cannot measure the
electric charge using the ampere. So option (A) is incorrect.
Option (B) 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
charge using the volt. So option (B) is incorrect.
Option (C) 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 charge. Hence, we cannot measure the
electric charge using the joule. So option (C) is incorrect.
This leaves us with option (D), the
coulomb. The coulomb is a unit that was
defined to help scientists describe the charge of particles like protons and
electrons. The definition of the coulomb is
based on the fact that the electron has an electric charge of roughly negative 1.6
multiplied by 10 to the power of negative 19 coulombs. Because electric charge is measured
using coulombs, option (D) is the correct answer.
The coulomb is the correct unit for
electric charge.
