A typical adult ear has a surface area of 2.1 Times 10^-3 m^2. The sound intensi

Question

A typical adult ear has a surface area of 2.1 Times 10^-3 m^2. The sound intensity during a normal conversation is about 3.2 Times 10^-6 W/m^2 at the listener's ear. Assuming that the sound strikes the surface of the car perpendicularly, how much power is by the ear? What is the ration of the given intensity to the reference intensity of 1 pW/m^2 (10^-22 W/m^2)? What is the corresponding sound level in decibels? A tiny ball whose mass is 0.0012 kg carries a charge of -18 mu C. What force is needed to cause the ball to float? How can it be generated? What are the magnitude and direction of the electric field executing this force? If the charge were to move at a constant velocity of 2,000 m/s, what value of the magnetic field strength, B, would be necessary to generate a magnetic force on this charge equal to the magnitude of the electric force? A 10-turn circular loop of radius 20 cm is placed in a localized magnetic field of strength 0.20 T so that the plane of the loop is perpendicular to the field. The direction of the magnetic field is into the paper. What is the flux through the loop? Does anything happen inside the loop as this placement ?

Explanation / Answer

1) a) Power = intensity * area

=3.2*10^-6*2.1*10^-3

= 6.72*10^-9 W

b) Ratio = 3.2*10^-6/10^-12 = 3.2 *10^6

c) Sound level = 10 log(Ratio) = 10 log( 3.2 *10^6)

= 65.05 dB

2)a) Force required = mg = 0.0012*9.8

= 0.01176 N

This can be done by applying electric field in downward direction

b) Eq =  0.01176 N

E =  0.01176/(18*10^-6)

= 653.33 N/C in downward direction

c) magnetic force = electrostatic force

qvB = qE

B= E/v = 653.33/2000

= 0.3267 T

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.