Answer:
Explanation:
Given that,
Frequency of a radio antenna is 1 MHz
Power, P = 21 kW
We need to find the the waves intensity 25 km from the antenna
. The object emits intenisty evenly in all direction. It can be given by :
So, the wave intensity 25 km from the antenna is 
.
If the transformer’s primary coil has 20 times as many turns of wire in it as the secondary coil has, then the secondary coil provides a small voltage rise for the large amount of current that flows through it.
Answer: Option B
<u>Explanation:</u>
A transformer has a two types of coils, the first one is primary coils and the second one is secondary coil. A secondary coils with hardly any turns in it provides the charges going through it just limited quantities of energy.
Without a long separation over which to do chip away at the charges streaming in the loop, the transformer delivers just a little ascent in the voltage of those charges. Be that as it may, the coil can give this little voltage to ascend to a huge current without requiring an excess of power supply from the input circuit.
