What is electrical resistivity? In a series electrical circuit comprising a resistor made up of a metallic wire, the ammeter reads $5\, A$. The reading of the ammeter decreases to half when the length of the wire is doubled. Why?

Draw a labelled circuit diagram showing three resistors $R_{1}, R_{2}$ and $R_{3}$ connected in series with a battery $(E)$,a rheostat $(Rh)$,a plug key $(K)$ and an ammeter $(A)$ using standard circuit symbols. Use this circuit to show that the same current flows through every part of the circuit. List two precautions you would observe while performing the experiment.

Find out the following in the electric circuit given in the figure:
$(a)$ Effective resistance of two $8\,\Omega$ resistors in the combination.
$(b)$ Current flowing through the $4\,\Omega$ resistor.
$(c)$ Potential difference across the $4\,\Omega$ resistor.
$(d)$ Power dissipated in the $4\,\Omega$ resistor.
$(e)$ Difference in ammeter readings,if any.

How can we measure the current in a circuit?

Give two practical applications of the heating effect of current.

Two electric circuits $I$ and $II$ are shown in the figure.
$(i)$ Which of the two circuits has more resistance?
$(ii)$ Through which circuit does more current pass?
$(iii)$ In which circuit is the potential difference across each resistor equal?