Answer:

Explanation:
give data:
inside diameter = 5.0 cm
charge q = 0.25 nC
Outside diameter = 15 cm
potential V at inside sphere is = 
potential V at outside sphere is = 
k is constant whose value is = 
then potential difference between two point is
![\Delta V = kq \left [\frac{1}{R}-\frac{1}{r} \right ]](https://tex.z-dn.net/?f=%5CDelta%20V%20%3D%20kq%20%5Cleft%20%5B%5Cfrac%7B1%7D%7BR%7D-%5Cfrac%7B1%7D%7Br%7D%20%20%5Cright%20%5D)
![\Delta V = 9*10^{9}*0.25*10^{-9} \left [\frac{1}{0.05}-\frac{1}{0.15} \right ]](https://tex.z-dn.net/?f=%5CDelta%20V%20%3D%209%2A10%5E%7B9%7D%2A0.25%2A10%5E%7B-9%7D%20%5Cleft%20%5B%5Cfrac%7B1%7D%7B0.05%7D-%5Cfrac%7B1%7D%7B0.15%7D%20%5Cright%20%5D)

Answer:
Total 20 number of resistors are required to connect in series
Explanation:
As we know by Ohm's law that potential difference across the resistor is the product of resistance and current flowing in it
So we have

here we know that
V = 120 V
i = 3 A
so we have

now we know that all the resistors are connected in series and each resistor is of 2 ohm
so total N number of resistors are required


The efficiency of the machine is 0.53 (53%).
Explanation:
The efficiency of a machine is given by:

where
is the output work
is the work in input
The output work is:

where
is the load
is the distance covered by the load
The input work is:

where
is the effort force
is the distance from the effort to the pivot
Solving for the efficiency,

So, the efficiency of the machine is 0.53 (53%).
Learn more about work:
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As we know that speed of sounds is given as

here we know that
t = 23 degree C
now from above equation we will have


now we also know that distance between two consecutive resonance length is half of the wavelength



now we know that


so frequency will be 786 Hz