In: Physics
a) The change in internal energy is
U =
Q + W
Where
Q is the change in heat energy and W is the work done.
The change in internal energy of the universe is equal to the
change in heat energy of the universe since the work done is
zero.
U =
Q
When the current is passed through the resistor, joules heating
effect happens and the energy released to the universe is
Q = I2 R t
Where I is current, R is the resistance and t is the time for which
the current is passed.
U = I2 R t = 102 x 100 x 300 s
U = 3 x 106 J
b) The Helmholtz free energy is
F =
U - TS
Where
S is the change in entropy of the universe.
The entropy change of the universe,
S =
Q / T
F =
U - T x (
Q / T)
F =
U - Q
= 3 x 106 J - 3 x 106 J = 0
F = 0
The change in Helmholtz free energy is zero.