Across a metallic conductor of non-uniform cross section a constant potential difference is applied. The quantity which remains constant along the conductor is

A, B and C are voltmeters of resistance R, 1.5 R and 3R respectively as shown in the figure. When some potential difference is applied between X and Y, the voltmeter readings are V_A, V_B and V_C respectively, Then

A potentiometer wire has length 4 m and resistance 8 $$\Omega $$. The resistance that must be connected in series with the wire and an accumulator of e.m.f. 2 V, so as to get a potential gradient 1 mV per cm on the wire is

The resistances in the two arms of the meter bridge are 5 $$\Omega $$ and R$$\Omega $$ respectively. When the resistance R is shunted with an equal resistance, the new balance point is at 1.6$$l$$₁. The resistance R is