The energies required to set up in a cube of side 10   cm , ( a ) A uniform electric field of 10 7   V   m - 1 and ( b ) A uniform magnetic field if 0 . 25   Wb   m - 2 , are respectively about μ 0 = 4 π × 10 - 7   H   m - 1 , ϵ 0 = 8 . 9 × 10 - 12   F   m - 1

Step-by-step solution

Recall the formula of energy in terms of electric field and magnetic field strength, E E = 1 2 ε 0 E 2 V   &   E B = 1 2 ε 0 B c 2 V ⇒ E E = 1 2 ε 0 E 2 V   ⇒ E E = 1 2 × 8 . 9 × 10 - 12 × 10 7 2 × 10 - 3 = 0 . 445   J ⇒ E B = 1 2 ε 0 B c 2 V ⇒ E B = 1 2 × 8 . 9 × 10 - 12 × 0 . 25 2 × 3 × 10 8 2 × 10 - 3 = 25   J