False Statement: SCR is a bidirectional device

Explanation:

1. Introduction to SCR:
SCR stands for Silicon Controlled Rectifier, which is a four-layer, three-terminal semiconductor device. It is a type of thyristor and is widely used in various power applications.

2. Bidirectional Device:
A bidirectional device is capable of conducting current in both directions. In other words, it allows the flow of current in either polarity. However, an SCR is not a bidirectional device as it can only conduct current in one direction.

3. Working Principle of SCR:
An SCR consists of three terminals: Anode (A), Cathode (K), and Gate (G). It operates based on the principle of rectification and control.

When a positive voltage is applied between the anode and cathode terminals, the SCR remains in the OFF state. However, if a positive voltage is applied between the gate and cathode terminals, it triggers the SCR into the ON state, allowing the current to flow through it.

4. Controlled Device:
An SCR is a controlled device as its conduction can be controlled by applying a gate signal. By varying the gate voltage, the SCR can be turned ON or OFF at desired instants, allowing control over the power flow.

5. Controlling Terminal:
In an SCR, the gate terminal acts as the controlling terminal. By applying a gate signal, the state of the SCR can be changed from OFF to ON, and vice versa.

6. High-Power Applications:
SCRs are commonly used in high-power applications due to their ability to handle large currents and voltages. They are used in various applications such as motor control, power supplies, lighting control, heating control, and voltage regulation.

Conclusion:
The false statement is option 'A' - SCR is a bidirectional device. SCR is a controlled device, where the gate terminal acts as the controlling terminal. It is widely used in high-power applications due to its ability to handle large currents and voltages.