(Solved): Problem 28-64a: A circuit consists of a large electromagnet that has an inductance of 54.0H and a r ...

Problem 28-64a: A circuit consists of a large electromagnet that has an inductance of $54.0\mathrm{H}$ and a resistance of $7.80?$, a dc $250\mathrm{V}$ power source, and an open switch - all connected in series. How long after the switch is closed is the current equal to $10.2\mathrm{A}$ ? Tries $0/15$ Problem 28-64b: How long after the switch is closed is the current equal to $31.5\mathrm{A}$ ? Tries $0/15$