Step 1: Write the given data.
Inductance is
\[
L=\frac{1}{6\pi}\ \text{H}.
\]
Resistance is
\[
R=15\ \Omega.
\]
Applied AC voltage is
\[
V=100\ \text{V}.
\]
Frequency is
\[
f=60\ \text{Hz}.
\]
Step 2: Find the inductive reactance.
The inductive reactance is
\[
X_L=2\pi fL.
\]
Substituting the values,
\[
X_L=2\pi(60)\left(\frac{1}{6\pi}\right).
\]
\[
X_L=\frac{120\pi}{6\pi}.
\]
\[
X_L=20\ \Omega.
\]
Step 3: Find the impedance of the \(R-L\) circuit.
For a series \(R-L\) circuit,
\[
Z=\sqrt{R^2+X_L^2}.
\]
So,
\[
Z=\sqrt{15^2+20^2}.
\]
\[
Z=\sqrt{225+400}.
\]
\[
Z=\sqrt{625}.
\]
\[
Z=25\ \Omega.
\]
Step 4: Find the current in the circuit.
Current is
\[
I=\frac{V}{Z}.
\]
\[
I=\frac{100}{25}.
\]
\[
I=4\ \text{A}.
\]
Step 5: Find the phase difference.
For a series \(R-L\) circuit, the phase angle \(\phi\) is given by
\[
\tan\phi=\frac{X_L}{R}.
\]
Therefore,
\[
\tan\phi=\frac{20}{15}.
\]
\[
\tan\phi=\frac{4}{3}.
\]
Hence,
\[
\phi=\tan^{-1}\left(\frac{4}{3}\right).
\]
Step 6: Final conclusion.
Therefore, the current and phase difference are respectively
\[
\boxed{4\ \text{A}\ \text{and}\ \tan^{-1}\left(\frac{4}{3}\right)}
\]
Hence, the correct option is
\[
\boxed{(3)}
\]