Question

In a vacuum diode, the space around the cathode which is filled with electrons, is called ________ .

• A. space charge
• B. electric field
• C. magnetic field
• D. electron cloud

Answer 1

The correct option is A space charge

A

The large number of free electrons emitted from the cathode is builds up at one place near the cathode and forms a cloud of free electrons. Thus cloud of free electrons near the cathode is called space charge. Due to this space charge, the further emitted electrons come back to the cathode hence no virtual emission takes place hence no current flows in the circuit.