Physics WebAssign Ch20 #13

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An electromagnet can be modeled as an inductor in series with a resistor. Consider a large electromagnet of inductance L = 12.5 H and resistance R = 6.00 Ω connected to a 18.0-V battery and switch as in the figure shown below. After the switch is closed, find the following.

(a) the maximum current carried by the electromagnet
_____A

(b) the time constant of the circuit
_____s

(c) the time it takes the current to reach 95.0% of its maximum value
_____s

[shanenieves]

Should it be ln (0.05) since it is 1-0.95?