Q17: The coefficient of linear expansion of steel is a = 11 x 10-6 / °C. A steel ball has a volume of exactly 100 cm3 at 0°C. When heated to 100°C, its
volume becomes in (cm3):
A
B
D
E
100.33
100.11
100.0011
100.0033
None of them

Solution:

The coefficient of volume expansion

p = ΔV/V1Δt

3a = V2-V1/V1Δt

Given

a = = 11 x 10-6 / °C

V2 is the final volume

V1 is the initial volume = 100cm³

Δt = 100-0 = 100°C

Substitute

3(11 x 10-6) = V2-100/100(100)

33*10^-6 * 10000 = V2-100

33*10^-2 = V2-100

V2 = 100 + 0.33

V2 = 100.33

Hence the new volume is 100.33cm³

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

distance = 150m

displ = root (50 ^2 + 100^2)

root(2500+10000)

root 125000