Distilled water acts as ........ for electricity.

Define resistance of a conductor. State the factors on which resistance of a conductor depends. Name the device which is often used to change the resistance without changing the voltage source in an electric circuit.
Calculate the resistance of $50 \, m$ length of wire of cross-sectional area $0.01 \, mm^2$ and of resistivity $5 \times 10^{-8} \, \Omega \, m$.

In an experimental set-up as shown below,a piece of silver was placed touching points $A$ and $B$. Next time it was replaced by a piece of wood. In which case did the bulb glow? Give reason to justify the observation.

Find the equivalent resistance across the two ends $A$ and $B$ of this circuit.

Three $2 \,\Omega$ resistors,$A, B$ and $C,$ are connected as shown in the figure. Each of them dissipates energy and can withstand a maximum power of $18 \,W$ without melting. Find the maximum current $I$ that can flow through the circuit.

You are given three equal resistors. The number of resistances which can be obtained by joining them in series and in parallel grouping is