The magnitude of this current can be controlled by a voltage applied between the cathode and the grid. The grid acts like a gate for the electrons. A more negative voltage on the grid will repel some of the electrons, so fewer get through to the anode, reducing the anode current. A positive voltage on the grid will attract more electrons from the cathode, so more reach the anode, increasing the anode current. Therefore, a low power varying (AC) signal applied to the grid can control a much more powerful anode current, resulting in amplification. Variation in the grid voltage will cause identical proportional variations in the anode current. By placing a suitable load resistance in the anode circuit, the varying current will cause a varying voltage across the resistance which can be much larger than the input voltage variations, resulting in voltage gain.