Answer:
(a) 
(b) The charge inside the shell is placed at the center of the sphere and negatively charged.
Explanation:
Gauss’ Law can be used to determine the system.

This is the net charge inside the sphere which causes the Electric field at the surface of the shell. Since the E-field is constant over the shell, then this charge is at the center and negatively charged because the E-field is radially inward.
The negative charge at the center attracts the same amount of positive charge at the surface of the shell.
Answer:
Power = 130 watt
Explanation:
Power is described as the ability to do work, it is also defined as the amount of work in Joules done in a given time in seconds. Mathematically, it is represented as:

In this example, power is calculated as follows:
Work = 39000 J
Time = 5 minutes
converting the time from minutes to seconds:
1 minute = 60 seconds
∴ 5 minutes = 60 × 5 = 300 seconds

N:B the unit for power can also be represented as Joules/seconds or J/s or JS⁻¹
Answer:
Sorry for being late. Hope this helps
Explanation:
The first harmonic would be the smallest frequency for a string to produce a standing wave. In addition, the strings were fixed in a single attachment and have only limited motion. It is because standing waves require a specific medium for the sound to travel in it.