The electromagnetic wave that delivers a cellular phone call to a car has a magnetic field with an rms value of 1.7 × 10-10 T. The wave passes perpendicularly through an open window, the area of which is 0.23 m2. How much energy does this wave carry through the window during a 44-s phone call?
To calculate the energy carried by the electromagnetic wave, we can use the formula:
Energy = Magnetic Field (B) x Area (A) x Time (t)
Given:
Magnetic Field (B) = 1.7 × 10-10 T
Area (A) = 0.23 m2
Time (t) = 44 s
We need to convert the magnetic field which is in tesla (T) to the standard unit of magnetic field, which is the gauss (G). Since 1 tesla is equal to 10,000 gauss, we can convert 1.7 × 10-10 T to gauss:
1.7 × 10-10 T x 10,000 G/T = 1.7 x 10-6 G
Now we can calculate the energy:
Energy = (1.7 x 10-6 G) x (0.23 m2) x (44 s)
Energy = (3.91 x 10-7 G.m2/s) x (44 s)
Energy = 1.72 x 10-5 G.m2
So, the energy carried by the wave through the window during a 44-second call is 1.72 x 10-5 G.m2.