For resistors in series:

$\overline{){{\mathbf{R}}}_{\mathbf{e}\mathbf{q}}{\mathbf{=}}{{\mathbf{R}}}_{{\mathbf{1}}}{\mathbf{+}}{{\mathbf{R}}}_{{\mathbf{2}}}{\mathbf{}}{\mathbf{.}}{\mathbf{.}}{\mathbf{.}}{\mathbf{}}{\mathbf{+}}{\mathbf{}}{{\mathbf{R}}}_{{\mathbf{n}}}}$

Ohm's law:

$\overline{){\mathbf{V}}{\mathbf{=}}{\mathbf{i}}{\mathbf{R}}}$

The inductor acts as a path of infinite resistance (open circuit) immediately after the switch is closed.

The switch in the figure has been open for a long time. It is closed at t = 0 s.

What is the current through the 20 ohm resistor immediately after the switch is closed?

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