How much energy is stored in a room 3.0 m by 4.0 m by 2.4 m due to the earth's magnetic field with a strength of 5.0 × 10^-5 T? (μ₀ = 4π × 10^-7 T • m/A) A) 570 mJ B) 29 mJ C) 10 mJ D) 100 mJ E) 57 mJ

Question

Quizplus · Accepted Answer

The energy stored in a magnetic field can be calculated using the formula:
E = (1/2) μ V H^2
where μ is the permeability of free space, V is the volume of the room, and H is the strength of the magnetic field.

Substituting the given values, we get:
E = (1/2) (4π × 10^-7 T•m/A) (3.0 m × 4.0 m × 2.4 m) (5.0 × 10^-5 T)^2
E = 2.9 × 10^-2 J
Converting to millijoules, we get:
E = 29 mJ

Therefore, the best choice is B, which corresponds to 29 mJ.

How Much Energy Is Stored in a Room 3