The Q-meter works on the principle of

A dc potentiometer is designed to measure up to about 2V with a slide wire of 300 mm. A standard cell of EMF 1.18 V obtains balance at 600 mm. A test cell is seen to obtain balance at 680 mm. The EMF of the test cell is

A reading of 120 is obtained when a standard inductor was connected in the circuit of a Q-meter and the variable capacitor is adjusted to a value of 300pF. A lossless capacitor of unknown value  is then connected in parallel with the variable capacitor and the same reading was obtained when the variable capacitor is readjusted to a value of 200pF. The value of  in pF is

Figure shows the input attenuator of a multimeter. The meter reads full scale with 12V at M, with the range switch at position ‘q’. What is the required voltage at M to obtain full-scale deflection with the range switch at position‘s’?

In d.c. potentiometer measurements, a second reading is often taken after reversing the polarities of the d.c. supply and the unknown voltage, and the average of the two reading is taken. This is with a view to eliminate the effects of