A block of mass M is suspended from two identical springs of negligible mass, spring constant k, and unstretched length L. First one spring is attached to the end of the other spring. The block is then attached to the second spring and slowly lowered to its equilibrium position. The two springs stretched a total distance of X1. Next, the springs are hung side by side. The block is then attached to the end of springs and again slowly lowered to its equilibrium position. The springs each stretch a distance of X2. Which of the following correctly shows the relationship between X1 and X2.
(A)X1=X2
(B)X1=√2X2
(C)X1=2X2
(D)X1=4X2
(E)X1=8X2

i guess that visual aids present persuasive examples to what you are presenting, some factors would be theme (does it fit with the color, information, what you are presenting), size (can you see it, is it a big enough span of data/information), and overall look of the visual aid.

hope this : )

adding a(n) to an electric circuit would increase the magnetic field around a wire;

b. solenoid

a solenoid is a type of electromagnet whose purpose is to generate a controlled magnetic field.

if the purpose of the solenoid is instead to impede changes in the electric current, a solenoid can be more specifically classified as an inductor rather than an electromagnet.

electromagnetic shielding is the practice of reducing the electromagnetic field in a space by blocking the field with barriers made of conductive or magnetic materials. shielding is typically applied to enclosures to isolate electrical devices from their surroundings, and to cables to isolate wires from the environment through which the cable runs. electromagnetic shielding that blocks radio frequency electromagnetic radiation is also known as rf shielding.

the shielding can reduce the coupling of radio waves, electromagnetic fields and electrostatic fields. a conductive enclosure used to block electrostatic fields is also known as a faraday cage. the amount of reduction depends very much upon the material used, its thickness, the size of the shielded volume and the frequency of the fields of interest and the size, shape and orientation of apertures in a shield to an incident electromagnetic

from wikipedia