Estimate the peak electric field inside a 1.2-kW microwave oven under the simplifying approximation that the microwaves propagate as a plane wave through the oven's 700-cm2 cross-sectional area.

Respuesta :

Answer:

The peak electric field is  [tex]E_o = 3593.6 V/m[/tex]

Explanation:

From the question we are told that

     The power is  [tex]P = 1.2 \ kW = 1.2 *10^{3} \ W[/tex]

     The cross-sectional area is  [tex]A = 700 \ cm^2 = 700 *10^{-4} \ m^2[/tex]

Generally the average intensity of the  microwave is mathematically represented as

      [tex]I = \frac{c * \epsilon _o * E_o^2 }{2}[/tex]

Where  [tex]c[/tex] is the speed of light with value  [tex]c = 3.0 *10^{8} \ m/s[/tex]

     and  [tex]\epsilon_o[/tex] is the permitivity of free space with value [tex]\epsilon_o = 8.85*10^{-12} \ m^{-3} \cdot kg^{-1}\cdot s^4 \cdot A^2[/tex]

   also [tex]E_o[/tex] is the peak electric field.

Now making [tex]E_o[/tex] the subject [tex]E_o = \sqrt{\frac{2 * I }{ c * \epsilon _o } }[/tex]

But this intensity of the  microwave can also be represented mathematically as

       [tex]I = \frac{ P }{A }[/tex]

substituting values

      [tex]I = \frac{ 1.2 *10^{3} }{700 *10^{-4} }[/tex]]  

      [tex]I = 17142.85 \ W/m^2[/tex]

So

      [tex]E_o = \sqrt{\frac{2 * 17142.85 }{ 3.0*10^{8}] * 8.85*10^{-12} } }[/tex]

      [tex]E_o = 3593.6 V/m[/tex]

The peak electric field of the microwave is 3,593.1 V/m.

The given parameters;

  • power of the wave, P = 1.2 kW = 1,200 W
  • area of the plane, A = 700 cm²

The intensity of the wave is calculated as follows;

[tex]I = \frac{P}{A} \\\\I = \frac{1,200}{700 \times 10^{-4}} \\\\I = 17,142.86 \ W/m^2[/tex]

The peak electric field is calculated as follows;

[tex]E_o = \sqrt{\frac{2I}{c \varepsilon _o} } \\\\E_o = \sqrt{\frac{2\times 17,142.86}{3\times 10^8 \times 8.85 \times 10^{-12}} } \\\\E_o = 3,593.1 \ V/m[/tex]

Thus, the peak electric field of the microwave is 3,593.1 V/m.

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