Which letter represents the location of the resister in this diagram? A B C D
2 answers:
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Answer:
a) ΔEC=-23.4kW
b)W=12106.2kW
c)
Explanation:
A)
The kinetic energy is defined as:
(vel is the velocity, to differentiate with v, specific volume).
The kinetic energy change will be: Δ ()=
Δ ()=
Where 1 and 2 subscripts mean initial and final state respectively.
Δ()=
This amount is negative because the steam is losing that energy.
B)
Consider the energy balance, with a neglective height difference: The energy that enters to the turbine (which is in the steam) is the same that goes out (which is in the steam and in the work done).
We already know the last quantity: =
Δ (
)=23400W
For the steam enthalpies, review the steam tables (I attach the ones that I used); according to that,
The exit state is a liquid-vapor mixture, so its enthalpy is:
Finally, the work can be obtained:
C) For the area, consider the equation of mass flow:
where
is the density, and A the area. The density is the inverse of the specific volume, so
The specific volume of the inlet steam can be read also from the steam tables, and its value is: , so:
COMPLETE QUESTION:
<em>When the magnetic flux through a single loop of wire increases by </em>30 Tm^2<em> , an average current of 40 A is induced in the wire. Assuming that the wire has a resistance of </em><em>2.5 ohms </em><em>, (a) over what period of time did the flux increase? (b) If the current had been only 20 A, how long would the flux increase have taken?</em>
Answer:
(a). The time period is 0.3s.
(b). The time period is 0.6s.
Explanation:
Faraday's law says that for one loop of wire the emf is
and since from Ohm's law
,
then equation (1) becomes
(a).
We are told that the change in magnetic flux is , the current induced is
, and the resistance of the wire is
; therefore, equation (2) gives
which we solve for to get:
,
which is the period of time over which the magnetic flux increased.
(b).
Now, if the current had been , then equation (2) would give
which is a longer time interval than what we got in part a, which is understandable because in part a the rate of change of flux is greater than in part b, and therefore , the current in (a) is greater than in (b).