To construct a voltmeter using a galvanometer with a coil resistance of 50 ohms that deflects full scale at 3.5 mA, a series resistance must be calculated to allow for a full-scale deflection at 35 volts. The required series resistance can be determined using Ohm's law, where the total voltage (35 V) equals the current (3.5 mA) multiplied by the total resistance (galvanometer resistance plus series resistance). Additionally, the discussion highlights the importance of understanding the principles of ammeters and voltmeters, as well as the behavior of capacitors in parallel for related problems. Participants are encouraged to reference their textbooks for guidance on these concepts. The thread emphasizes the need for a clear understanding of voltage and resistance relationships in circuit design.