Answer:
Explanation:
The answer is electric field intensity. Electric field intensity is the force per unit positive charge which the charge exerts at any point.
We get the clearest image if there is no magnification. When we have no magnification the image and real object have the same size.
If we look at the diagram that I attached we can see that:

Two triangles that I marked are similar and from this we get:

The image and the object must have the same height so we get:

This tells how far the screen should be from the lens.
The position of the screen on the optical bench is:
Answer:
I = 4.75 A
Explanation:
To find the current in the wire you use the following relation:
(1)
E: electric field E(t)=0.0004t2−0.0001t+0.0004
ρ: resistivity of the material = 2.75×10−8 ohm-meters
J: current density
The current density is also given by:
(2)
I: current
A: cross area of the wire = π(d/2)^2
d: diameter of the wire = 0.205 cm = 0.00205 m
You replace the equation (2) into the equation (1), and you solve for the current I:

Next, you replace for all variables:

hence, the current in the wire is 4.75A
Answer:
a) 
b) 
c) Compressing is easier
Explanation:
Given:
Expression of force:

where:



when the spring is stretched
when the spring is compressed
hence,

a)
From the work energy equivalence the work done is equal to the spring potential energy:
here the spring is stretched so, 
Now,
The spring constant at this instant:



Now work done:



b)
When compressing the spring by 0.05 m
we have, 
<u>The spring constant at this instant:</u>



Now work done:



c)
Since the work done in case of stretching the spring is greater in magnitude than the work done in compressing the spring through the same deflection. So, the compression of the spring is easier than its stretching.
Answer:
0.01154 A
Explanation:
We have given the energy in the magnetic field
Value of inductance L =0.060 H
Energy stored in magnetic field is given by 


So the current flowing through rectangular toroid will be 0.01154 A