Question

The magnetic potential energy stored in a certain inductor is 25 mJ, when no current in the inductor is 60 mA.The inductance is ?


NEET 2018

Answer 1

Hello Dear.

Here is the answer---

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Given ⇒   

Magnetic Potential Energy(U) = 25 mJ.
                                               = 25 × 10⁻³ J.

Current Flowing in the Inductor(I) = 60 mA.
                                                         = 60 × 10⁻³ A.

Using the Formula,

           U = (1/2) L × I²
⇒ 25 × 10⁻³ = (1/2) L × (60 × 10⁻³)²
⇒ L = (50 × 10⁻³) ÷ (3600 × 10⁻⁶)
⇒ L = (50 × 10³) ÷ 3600
⇒ L = 13.89 H.


∴ The Inductance of the Inductor is 13.89 H.


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Hope it helps.

Have a Good Day.

Answer 2

∵ magnetic potrn energy stored in inductor is given by
E = 1/2 L i² , Where , L is inductance of inductor, i is current in inductor

Given,
E = 25 mJ = 25 × 10⁻³ J
i = 60mA = 60 × 10⁻³ A
∴ 25 × 10⁻³ = 1/2 × L × (60 × 10⁻³)²
⇒ 25 × 10³ = 1800 L
⇒L = 25000/1800 = 250/18 = 13.88 Henry

Hence, inductance = 13.88 H