BS1.1 Bridge Rectifier

Working of the Circuit

# During the positive half cycle of secondary voltage, diodes D2 and D3 are

   forward biased and diodes D1 and D4 are reverse biased Now the current

   flows through D2-->Load-->D3

# During the negative half cycle of the secondary voltage, diodes D1 and D4

   are forward biased and diodes D2 and D3 are reverse biased Now the current

   flows through D4-->Load-->D1

# In both cycle the load current flows in same direction hence we get a

   Pulsating DC voltage as shown in fig (2)

fig (1) Input Sine wave      

fig (2) Pulsating DC output

# The capacitor is used for converting the pulsating DC voltage to fixed DC

   voltage.

# Up to t=1s input is increasing, so the capacitor charged up to peak value of

   the input. After t=1s input starts to decrease then the voltage across the

   capacitor reverse biases the diodes D2 and D4 hence it will not conduct now

   capacitor discharges through the load, then voltage across the capacitor

   decreases

# When the peak voltage exceeds the capacitor voltage, Diode D2 or D4

   forward biases accordingly as a result capacitor again charges to the peak

   value. This process continues. Hence we get almost smooth DC voltage as

   shown in fig (3)

fig (3) Constant DC output

# i-St@r Tips: 
   You can use Step down Center tapped transformer as well as ordinary Step
   down transformer. If you choose Center tapped transformer it is possible to
   change the output DC. 
   By connecting middle point and a terminal point of transformer to the 
   rectifier or connecting both terminal points of transformer to the rectifier 
   circuit voltage can be changed.