# Investigatory Project on Bridge Rectifier

**INVESTIGATORY PROJECT ON THE
BRIDGE RECTIFIER**

**Aim:** To construct a bridge rectifier
using four identical diodes and to calculate its ripple factor with and without
filtering.

**Materials
and Apparatus**

(i) Four
identical diodes

(ii) An
electrolytic condenser 500µF or 1000 µF, a condenser
0.1 µF

(iii)
Resistance 1000Ω

(iv) A step down
transformer with 220 to 240 V primary and 6.3 V, 100mA secondary

(v) ac and dc
voltmeters or a multimeter etc.

(vi) CRO

**Working**

During the
positive half cycles of the secondary voltage in the circuit, the diodes D_{2 }and D_{4}
would conduct current and the diodes D_{1} and D_{3} would not conduct.
Therefore, the current flows through the secondary winding of the transformer to the diode D_{2}, then Load resistor R_{L} and through the diode D_{4}. During the negative half
cycles in the circuit, the diodes D_{1} and D_{3} would conduct and the diodes D_{2}
and D_{4} would not conduct. Therefore, current flows through the
secondary winding of the transformer to the diode D_{3}, then load resistor R_{L} and through the diode D_{1}.
In both cases, the current passes through the R_{L} in the same direction.

**Procedure**

1. Wire the
Bridge rectifier circuit without capacitor after testing all the components.

2. Switch
ON the mains supply to generate current. Observe the Secondary Voltage waveform from the transformer and and also the output
voltage waveform across R_{L}, simultaneously on CRO Screen. Note down peak
values.

3.
Calculate the ripple factor using the expression.

4. Connect
the capacitor filter and observe the waveforms. Calculate the ripple factor
using the expression.

5. Connections
are made as shown in the figure. D_{1}, D_{2}, D_{3}
and D_{4} are four identical diodes, C is a 500 µF or 1000 µF electrolytic condenser, C’ is a
0.1µF condenser. R_{L} is 1kΩ resistor. The rectified output is obtained across R_{L}.

**(a) To find the ripple
factor (r) with filter circuit**

Specification
of the diodes (from data book)

Type number
of the diode: ............

Maximum
forward current rating = ............mA

PIV rating
= .........V

The ac
output voltage V_{ac }is measured by an ac voltmeter or by a multimeter
across the points T_{3} and T_{4}. The dc output voltage V_{dc}
is measured between the point T_{1} and T_{2}. The ripple
factor is calculated by the equation,

r = V_{ac}/V_{dc}

ac output
voltage = V_{ac} = ........V

dc output
voltage = V_{dc} = ........V

Ripple
Factor, r = V_{ac}/V_{dc} = .........

**(b) To find
the ripple factor (r) without the filter circuit**

The filter
circuit is removed by disconnecting the condenser C from the above figure. The
ripple factor is determined as explained above.

ac output voltage = V_{ac} = ........V

dc output
voltage = V_{dc} = ........V

Ripple
Factor, r = V_{ac}/V_{dc} = .........

**Result:**

The ripple
factor of the bridge rectifier:

(a) with
the filter circuit = ......

(b) without
the filter circuit = ......

**Note:**
Ripple factor r may be calculated for different loads R_{L}; and a
graph with r and R_{L} may be drawn.

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