In the first orbit of hydrogen the radius is 0.529 × 10⁻¹⁰ m and the speed is 2.19 × 10⁶ m/s…

Step 1. One turn. $T = \dfrac{2\pi r}{v} = \dfrac{2\pi \times 0.529 \times 10^{-10}\ \text{m}}{2.19 \times 10^{6}\ \text{m/s}} = 1.52 \times 10^{-16}\ \text{s}$.

Step 2. Turns each second. $f = \dfrac{1}{T} = 6.59 \times 10^{15}\ \text{s}^{-1}$.

Step 3. Current. $I = ef = 1.6 \times 10^{-19}\ \text{C} \times 6.59 \times 10^{15}\ \text{s}^{-1} = 1.05 \times 10^{-3}\ \text{A}$, which is $1.05\ \text{mA}$.