The change in the strength of the current flowing through the electron lamp in the laboratory installation is performed... 2) ...by changing the voltage between the cathode and the lamp grid. 4) ...changing the lamp type. 8) ...by changing the temperature of the cathode. Specify the correct approval number.

The correct answer is 2)...by changing the voltage between the cathode and the lamp grid.<br /><br />The strength of the current flowing through an electron lamp in a laboratory installation can be changed by adjusting the voltage between the cathode and the lamp grid. This is because the current in an electron lamp is directly proportional to the voltage applied across the lamp. By increasing or decreasing the voltage, the current flowing through the lamp can be increased or decreased respectively.<br /><br />Changing the lamp type (option 4) would not directly affect the strength of the current flowing through the lamp. The type of lamp may affect the overall performance of the lamp, but it does not directly control the current.<br /><br />Changing the temperature of the cathode (option 8) may affect the emission of electrons from the cathode, but it does not directly control the strength of the current flowing through the lamp. The temperature of the cathode may affect the overall performance of the lamp, but it does not directly control the current.<br /><br />Therefore, the correct answer is 2)...by changing the voltage between the cathode and the lamp grid.