Answer:
The first harmonic is: 250Hz, second harmonic 500Hz, third harmonic 750Hz.
Explanation:
Use the frequency f, speed v, and wavelentgh L relationship:

We are given the speed v=400 m/s. The base wavelength on a string of length 80cm is twice the length of the string (a "half wave" along the full length of the string), so:

The fundamental frequency (first harmonic) is 250 Hz
The second harmonic is produced by one full wave across the string (adding one node in the middle), so L=80cm in this case, therefore the second harmonic frequency is: f2 = 2*250=500Hz
the third harmonic add another node (and a half wave) to the pattern and the wavelength will be 2/3 of 80cm, so f3=3*250Hz = 750Hz
Answer:
D. it demonstrates electromagnetism.
Explanation:
If a wire carrying current causes the needle of a compass to move, it is an example of electromagnetism.
The interaction between electric and magnetic fields is termed electromagnetism.
- Electromagnetic interaction is usually induced between a wire and bar magnet.
- With right set up magnetic and electrical fields can be induced using a magnet and current carrying wire.
P = VI
1000 Watts = 120*I
I = 1000/120
I = 8.3 amps
Option (3) is correct.....
s = d/t
Speed = Distance divided by time
1.55 × 10^3 would be the scientific notation