Suppose that e = 66.0 v , r = 230 ω and l = 0.170 h . with switch s2 open, switch s1 is left closed until a constant current is established. then s2 is closed and s1 opened, taking the battery out of the circuit. a: what is the initial current in the resistor, just after s2 is closed and s1 is opened? b: what is the current in the resistor at t = 4.50×10−4 s ? c: what is the potential difference between points b and c at t = 4.50×10−4 s ? d: which point is at a higher potential? e: how long does it take the current to decrease to half its initial value? university physics with moderen physics 14th edition