Answer:
The doorbell transforms electrical energy into sound.
Explanation:
The doorbell MAY turn electrical energy into motion of a striker which then impacts a resonator creating sound. However all door bells do not have solenoids. Some are electronic playing recordings when activated.
All doorbells do produce sound, though.
Answer:
A. 
B. 
C. 
Explanation:
The capacitance of a capacitor is its ability to store charges. For parallel-plate capacitors, this ability depends the material between the plates, the common plate area and the plate separation. The relationship is
is the capacitance, 
is the common plate area, 
is the plate separation and 
is the permittivity of the material between the plates.
For air or free space, is 
called the permittivity of free space. In general, 
where 
is the relative permittivity or dielectric constant of the material between the plates. It is a factor that determines the strength of the material compared to air. In fact, for air or vacuum, 
.
The energy stored in a capacitor is the average of the product of its charge and voltage.
Its charge, 
, is related to its capacitance by 
(this is the electrical definition of capacitance, a ratio of the charge to its voltage; the previous formula is the geometric definition). Substituting this in the formula for 
,
A. Substituting for in ,
B. When the distance is 
,
C. When the distance is restored but with a dielectric material of dielectric constant, 
, inserted, we have
The answer is B because solids have a definite shape and volume
The whistling sound from the hearing aids represents that your hearing aids is working perfectly ad is known as the "feedback". So, the given statement is true.
Answer: Option A
<u>Explanation:</u>
It's often sounds irritating when a hearing aids of your grandpa or Grandma whistles. especially, when they put them out of their ears. Actually, this feedback sound from hearing aids occur when the sounds from the outer side bounces back to the microphone of the hearing aids.
The sound bounces back when it doesn't gets inside of your ear canal so that one can hear the sound through the hearing aid. When the sounds bounces back in the hearing aid, it get re-amplified and thus we hear the whistle sound which is known as the feedback of the device.
It's not always the feedback sound though. Sometimes the device whistles when it has some mechanical defect or when one hugs the other one or water gets inside and damaged the whole system.
Answer:
the acceleration of the car is -4.9m/s2.
the direction is opposite to the actual direction, since the acceleration is negative.
