Two identical thermally insulated spherical tanks, A and B, are connected by a valve. Initially tank A contains 20mol of an ideal diatomic gas, tank B is evacuated, and the valve is closed. If the valve is opened and the gas expands isothermally fromA to B, what is the change in the entropy of the gas?

Explanation:

Volume of gas is doubled isothermally . Let the temperature of the gas be T .Work done by the gas

W = 2.303 nRT log 2 V / V

Since expansion is isothermal , Δ E = 0

Q = ΔE + W

Q = W

Q = 2.303 nRT log 2 V / V

Q / T = 2.303 n R log 2

Change in entropy = ΔS = Q / T = 2.303 n R log 2

= 2.303 x 20 x 8.3 x .3010 J T⁻¹.

= 115  J T⁻¹.

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