Question

An electromagnet has stored 648 J of magnetic energy, when a current of 9A exists in its coils. What average emf is induced if the current is reduced to zero in 0.45 s?
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Answer 1

Answer:

$\huge\underline\orange{\mathcal Answer}$

$\huge\underline{\mathcal Given}$

Magnetic Energy = 648 J

Current = 9 A

Time = 0.45 s

$\large{\boxed{\mathcal Magnetic\:energy(U)={\frac{1}{2}}L{I}^{2}}}$

$\large{\mathcal L={\frac{2U}{I^2}}}$

$\large{\mathcal L ={\frac{2×648}{9×9}}}$

$\huge{\boxed{\mathcal L=16H}}$

$\large{\boxed{\mathcal Induced\:emf(e)=L{\frac{dI}{dt}}}}$

$\large{\mathcal e =(16){\frac{9}{0.45}}}$

$\huge{\boxed{\mathcal emf(e)=320V}}$

$\huge\orange{\mathcal Hope\:it\:helps!!!}$