Answer:
C. Copper
Explanation:
F = Force on string
= Intial length of string
A = Area of string
E = Young's modulus of material
Change in length is given by

It can be seen that the change in length is inversely proportional to the Young's modulus of the material.
Here




So, copper will stretch the least.
Einstein's energy mass equivalence relation say that if the whole given mass is converted to energy then it would be

where
m = mass in kg
c = speed of light in m/s
this is the origination of quantum physics and by this formula we can relate the dual nature of light and particle
So correct relation above will be

Answer:

Explanation:
= Permittivity of free space = 
A = Area = 
d = Thickness = 
k = Dielectric constant = 5.4
V = Voltage = 86.2 mV
Charge is given by

The charge on the outer surface is 
A pair of scissors .....................................
Answer:
The magnitude of the force on the wire is 2.68 N.
Explanation:
Given that,
Length of the wire, L = 5 m
Magnetic field, B = 0.37 T
Angle between wire and the magnetic field, 
Current in the wire, I = 2.9 A
We need to find the magnitude of the force on the wire. The magnetic force in the wire is given by :

So, the magnitude of the force on the wire is 2.68 N. Hence, this is the required solution.