Final answer:
A bridge rectifier consists of four diodes arranged in a configuration that converts AC from a secondary coil to DC, exploiting the property of diodes to allow current to flow in only one direction.
Step-by-step explanation:
In a bridge rectifier, which is a type of circuit used to convert alternating current (AC) from a secondary coil to direct current (DC), you should expect to find four diodes. These diodes are arranged in a specific configuration that allows the rectifier to convert the AC input to DC output by allowing current to flow in only one direction. During each half-cycle of the AC, two of the diodes conduct, allowing current to pass through, while the other two block current, ensuring that the output is always of one polarity, effectively rectifying the AC into DC.
The principle of diode operation is based on allowing current to flow through it when the voltage across the diode is positive and above a certain threshold, typically around 0.7 V for silicon diodes. When the voltage is negative or below this threshold, the current flow through the diode is very limited. This characteristic is central to the function of a bridge rectifier.