Silicon Controlled Rectifiers

Germanium ✘ Silicon ✘ Carbon ✘ None of the above ✔

Gate ✘ Cathode ✘ Anode ✘ None of the above ✔

Voltage ✘ Current ✘ Voltage as well as current ✘ None of the above ✔

Positive half-cycles only ✘ Negative half-cycles only ✘ Both positive and negative half-cycles ✘ Positive or negative half-cycles ✔

At zero potential ✘ Negative ✘ Positive ✘ None of the above ✔

Two ✘ Three ✘ Four ✘ None of the above ✔

Positive ✘ Negative ✘ At zero potential ✘ None of the above ✔

Unidirectional ✘ Bidirectional ✘ Mechanical ✘ None of the above ✔

Triode ✘ Pentode ✘ Gas-filled triode ✘ Tetrode ✔

Changing anode voltage ✘ Changing gate voltage ✘ Reverse biasing the gate ✘ None of the above ✔