Joseph studied whether different materials can block certain electromagnetic waves by testing television reception in different
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Considering the Doppler efect, the frequency heard by the student would change if:
- if the student walked toward the police car.
- if the student walked away from the police car.
- if the police car moved toward the student.
- if the police car moved away from the student.
The Doppler effect is defined as the change in the apparent frequency of a wave produced by the relative motion of the source with respect to its observer. In other words, this effect is the change in the perceived frequency of any wave motion when the sender and receiver, or observer, move relative to each other.
The following expression is considered the general case of the Doppler effect:
Where:
- f', f: Frequency perceived by the receiver and frequency emitted by the transmitter, respectively. Its unit of measurement in the International System (S.I.) is the hertz (Hz), which is the inverse unit of the second (1 Hz = 1 s⁻¹)
- v: Wave propagation speed in the medium. It is constant and depends on the characteristics of the medium. In this case, the speed of sound in air is considered to be 343 m/s.
- vR, vE: Receiver and transmitter speed respectively. Its unit of measure in the S.I. is the m/s
- ±, ∓:
- We will use the + sign:
- In the numerator if the receiver approaches the sender
- In the denominator if the sender moves away from the receiver
- We will use the - sign:
- In the numerator if the receiver moves away from the sender
- In the denominator if the sender approaches the receiver
In summary, the Doppler Effect is an alteration of the observed frequency of a sound due to the movement of the source or the observer, that is, they are changes in the frequency and wavelength of a wave due to the relative movement between the wave source and the observer.
<h3>Changes on the frequency </h3>In this case, considering the Doppler effect, the frequency heard by the student would change if:
- if the student walked toward the police car.
- if the student walked away from the police car.
- if the police car moved toward the student.
- if the police car moved away from the student.
Learn more about Doppler effect:
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Answer:
The coil with the maximum number of loops will produce the magnetic field with the maximum strength.
Explanation:
The magnetic field produced by a current-carrying coil at a point on the axis which is passing through its center and perpendicular to its plane is given by
<em>where</em>,
= magnetic permeability of the free space.
- N = number of loops of the coil.
- I = current flowing through the coil.
- R = radius of the coil.
- r = distance of the point where the magnetic field is to be found from the center of the coil.
Now, it is given that all the four coils have the same size, means same radius R, same material, means same permeability for all the coils, and the same amount of current is passing through all the coils, means same current I.
The magnetic field of all the four coils is differing only due to the number of loops N.
Thus, the coil with the maximum number of loops N will produce the magnetic field with the maximum strength.