Cracking the SAT Physics Subject Test

Before we get to some examples, it’s worthwhile to introduce a new unit for
energy. The SI unit for energy is the joule, but it’s too large to be convenient in the
domains we’re studying now. We’ll use a much smaller unit, the electronvolt
(abbreviated eV). The eV is equal to the energy gained (or lost) by an electron
accelerated through a potential difference of one volt. Using the equation ∆UE =

q∆V, we find that

1 J = 6.24 × 10^18 eV

In terms of electronvolts, the value of Planck’s constant is 4.14 × 10−15

eV • s.

Questions 1-3