# 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.