The expression 1/2 ε₀E² represents energy density, which is defined as:

Energy density = Energy /Volume

Dimensions used:

• Energy = ML²T⁻²

• Volume = L³

Step 1: Find the dimensions of energy density.

Energy density = ML²T⁻² /L³

Step 2: Compare with given form M^aL^bT^c. =

a =1, b=−1, c=−2

Step 3: Compute required expression. a −2b+c=1−2(−1)+(−2)=1+2−2=1

Energy density problems can be solved quickly by remembering:

Energy density = ML⁻¹T⁻²

No need to derive each time in exams.