A block has dimensions $1 \mathrm{~cm}, 2 \mathrm{~cm}$ and 3 cm . Ratio of the maximum resistance to minimum resistance between any palr of opposite faces of the block is

A current of 6 A enters one corner $P$ of an equilateral triangle $P Q R$ having three wires of resistance $2 \Omega$ each and leaves by the corner $R$ as shown in figure. Then the currents $I_1$ and $I_2$ are respectively

The value of shunt resistance that allows only $10 \%$ of main current through the galvanometer of resistance $99 \Omega$ is

A steady current is flowing in a metallic conductor of non-uniform cross-section. The physical quantity which remains constant is