The inductance of the coil is approximately 0.044H.
The decay of current in an inductor is described by the formula I(t)=I0e^−R.t/L, where I(t) is the current at time t, I0 is the initial current, R is the resistance, L is the inductance, and t is time.
Given that the current (I) has decayed to 0.300 A at t=2.50 ms after the coil is opened, and assuming the initial current (I0) was higher, the time constant (τ) of the decay can be determined. The time constant is given by τ= L/R, where L is the inductance and R is the resistance.
From the given information, the time constant is calculated, and subsequently, the inductance (L) is found by rearranging the formula as L=τR. The calculated inductance is approximately 0.044H. This process involves understanding the behavior of an inductor in an RL circuit during the decay of current over time.