Concept:
Each physical law describes a specific electromagnetic phenomenon and is associated with a particular application:
• Ampere’s Law: Relates magnetic field to current.
• Biot-Savart Law: Calculates magnetic field due to a current element.
• Coulomb’s Law: Determines force between electric charges.
• Gauss’s Law: Relates electric flux to enclosed charge.
Step 1: Match Ampere’s Law
Ampere’s law gives the relationship between current and magnetic field:
\[
\oint \vec{B} \cdot d\vec{l} = \mu_0 I
\]
It is used to determine magnetic flux density.
\[
A \rightarrow IV
\]
Step 2: Match Biot-Savart Law
Biot-Savart law gives the magnetic field due to a small current element:
\[
d\vec{B} \propto \frac{I \, d\vec{l} \times \hat{r}}{r^2}
\]
It is used for calculating effects due to current-carrying conductors.
\[
B \rightarrow II
\]
Step 3: Match Coulomb’s Law
Coulomb’s law gives force between charges:
\[
F = k \frac{q_1 q_2}{r^2}
\]
\[
C \rightarrow I
\]
Step 4: Match Gauss’s Law
Gauss’s law:
\[
\oint \vec{E} \cdot d\vec{A} = \frac{Q}{\epsilon_0}
\]
It is used to determine electric flux density.
\[
D \rightarrow III
\]
Step 5: Final matching
\[
A-IV,\quad B-II,\quad C-I,\quad D-III
\]
\[
\therefore \text{Correct answer is (B)}
\]