Answer:
The electric current in the wire is 0.8 A
Explanation:
We solve this problem by applying the formula of the magnetic field generated at a distance by a long and straight conductor wire that carries electric current, as follows:

B= Magnetic field due to a straight and long wire that carries current
u= Free space permeability
I= Electrical current passing through the wire
a = Perpendicular distance from the wire to the point where the magnetic field is located
Magnetic Field Calculation
We cleared (I) of the formula (1):
Formula(2)

a =8cm=0.08m

We replace the known information in the formula (2)

I=0.8 A
Answer: The electric current in the wire is 0.8 A
Answer:
C is the right answer.
Body massager uses electrical energy to move back and forth. In this sense, a motor is being used for the operation
A. 409 Hz
The fundamental frequency of a string is given by:

where
L is the length of the wire
T is the tension in the wire
m is the mass of the wire
For the piano wire in this problem,
L = 0.400 m
T = 1070 N
m = 4.00 g = 0.004 kg
So the fundamental frequency is

B. 24
For this part, we need to analyze the different harmonics of the piano wire. The nth-harmonic of a string is given by

where
is the fundamental frequency.
Here in this case

A person is capable to hear frequencies up to

So the highest harmonics that can be heard by a human can be found as follows:

Answer:
0.94m/s (squared)
Explanation:
a=change in velocity/time
a=v-u/t
a=32-0=32/32
a=0.94m/s (squared)
Answer:
v = 2 cm/s
Explanation:
The equation of the wave is
y(x,t) = (2.0cm)*cos(2π*x−4π*t)
Where,
x is measured in cm
t in s
A more general formula for this equation would be
y(x,t) = A*cos(k*x−ω*t)
Where,
A = amplitude.
k = the wavenumber
ω = the angular frequency
The velocity of the wave corresponds to
v = ω/k
v = 4π / 2π = 2 cm/s
v = 2 cm/s