Design a half-wave recti er which provides a peak voltage of 15 V, and anaverage voltage of 3.8 V when driven by a 120 V (rms) a
c voltage supply
1 answer:
Answer:
You need a 120V to 24V commercial transformer (transformer 1:5), a 100 ohms resistance, a 1.5 K ohms resistance and a diode with a minimum forward current of 20 mA (could be 1N4148)
Step by step design:
- Because you have a 120V AC voltage supply you need an efficient way to reduce that voltage as much as possible before passing to the rectifier, for that I recommend a standard 120V to 24V transformer. 120 Vrms = 85 V and 24 Vrms = 17V = Vin
- Because 17V is not 15V you still need a voltage divider to step down that voltage, for that we use R1 = 100Ω and R2 = 1.3KΩ. You need to remember that more than 1 V is going to be in the diode, so for our calculation we need to consider it. Vf = (V*R2)/(R1+R2), V = Vin - 1 = 17-1 = 16V and Vf = 15, Choosing a fix resistance R1 = 100Ω and solving the equation we find R2 = 1.5KΩ
- Finally to select the diode you need to calculate two times the maximum current and that would be the forward current (If) of your diode. Imax = Vf/R2 = 10mA and If = 2*Imax = 20mA
Our circuit meet the average voltage (Va) specification:
Va = (15)/(pi) = 4.77V considering the diode voltage or 3.77V without considering it
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Answer:
Explanation:
According to the first thermodynamic law, the energy must be conserved so:
Where Q is the heat transmitted to the system, U is the internal energy and W is the work done by the system.
This equation can be solved by integration between an initial and a final state:
(1)
As per work definition:
For pressure the force F equials the pressure multiplied by the area of the piston, and considering dx as the displacement:
Here A*dx equals the differential volume of the piston, and considering that any increment in volume is a work done by the system, the sign is negative, so:
So the third integral in equation (1) is:
Considering the gas as ideal, the pressure can be calculated as , so:
In this particular case as the systems is closed and the temperature constant, n, R and T are constants:
Replacion this and solving equation (1) between state 1 and 2:
The internal energy depends only on the temperature of the gas, so there is no internal energy change , so the heat exchanged to the system equals the work done by the system:
