Bridge Full Wave Rectifier Peak Voltages and Capacitcane Value

[eximius]

Note: This is not a homework or coursework, simply revision for an exam. Thanks

Homework Statement

[PLAIN]http://img194.imageshack.us/img194/223/question2z.jpg

Homework Equations

Peak voltage = RMS voltage x root2
r = T/(2RlC)
T = 1/f

The Attempt at a Solution

part d)

Peak Supply Voltage = 240 x root2 = 339.41V
Peak Va = 339.41 x 0.1 = 33.941V
Peak Vb = 33.941 - 0.7 = 33.241V (uncertain about this one)

part e)

r=10%=0.1 T=1/50 Rl=200ohms

.:.

r = T/(2RlC)

0.1 = 0.02/400C
40C = 0.02
C = 5x10-4F

 

[SirAskalot]

d) You got 0.7V voltage drop over each diode. How many diodes do the current go trough per half period (one pulse)?

 

[eximius]

d) You got 0.7V voltage drop over each diode. How many diodes do the current go trough per half period (one pulse)?

Ahhh, so because it goes through 2 diodes there's a 1.4 V drop?

 

[SirAskalot]

You tell me...

Draw a simple diagram for one half period ( (?) diodes, eqv. voltage source, and load). 'Kirchhoff voltage law' will tell you the answer.

 

[eximius]

During one half period there is current flow through 2 of the diodes. In the positive half cycle there's current flow through D2 and D3. But looking at current flow diagrams has made me think that the Voltage drop at Vb is just 0.7 V. Because from Va to Vb there's only one diode.

I'm just uncertain. And I have no clue when it comes to KVL, haven't studied it yet.

 

[Adjuster]

During one half period there is current flow through 2 of the diodes. In the positive half cycle there's current flow through D2 and D3. But looking at current flow diagrams has made me think that the Voltage drop at Vb is just 0.7 V. Because from Va to Vb there's only one diode.

I'm just uncertain. And I have no clue when it comes to KVL, haven't studied it yet.

A basic statement of Kirchhoff's Voltage Law is that around any closed loop, the sum of the emfs is equal to the sum of potential drops. You need to grasp that idea if you want to make sense of circuits.

There is also a diode in the path leading to the bottom end of Rl. It too requires 0.7V across it to make it conduct. Where does that voltage come from?