I believe the answer is Microwaves (just to clarify, not the oven). They're widely used for communications.<span />
Answer:
Voltage in primary coil is 3.91 V
Explanation:
For transformer we know that the working principle is given as

here we know that
![V_1 [tex] = voltage in primary coil[tex]V_2 = 25 V](https://tex.z-dn.net/?f=V_1%20%5Btex%5D%20%3D%20voltage%20in%20primary%20coil%3C%2Fp%3E%3Cp%3E%5Btex%5DV_2%20%3D%2025%20V)


Now we have


Answer:
You will hear the note E₆
Explanation:
We know that:
Your speed = 88m/s
Original frequency = 1,046 Hz
Sound speed = 340 m/s
The Doppler effect says that:

Where:
f = original frequency
f' = new frequency
v = velocity of the sound wave
v0 = your velocity
vs = velocity of the source, in this case, the source is the diva, we assume that she does not move, so vs = 0.
Replacing the values that we know in the equation we have:

This frequency is close to the note E₆ (1,318.5 Hz)