# In the coil, the inductance of which is 0.6 H, there is an EMF of self-induction equal to 30 V.

In the coil, the inductance of which is 0.6 H, there is an EMF of self-induction equal to 30 V. Calculate the change in the current strength and energy of the magnetic field of the coil, if this happened in 0.2 s.

To calculate the values of the change in the current and energy of the magnetic field of the specified coil, we use the formulas: εi = L * ΔI / Δt, from where we express: ΔI = εi * Δt / L and ΔW = L * (Iк ^ 2 – Iн ^ 2) / 2 ( we will assume that the current in the coil has decreased to zero) = L * ΔI2 / 2.

Data: L – coil inductance (L = 0.6 H); εi – emerged EMF of self-induction (εi = 30 V); Δt – time change (Δt = 0.2 s).

Calculation: a) Change in current: ΔI = εi * Δt / L = 30 * 0.2 / 0.6 = 10 A;

b) Change in field energy: ΔW = L * ΔI ^ 2/2 = 0.6 * 10 ^ 2/2 = 30 J.

Answer: The current in the indicated coil has changed by 10 A; the energy of the magnetic field changed by 30 J.

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