Estimate the average drift speed of conduction electrons in a copper wire of cross-sectional area 2.5 × 10⁻⁷ m² carrying a current of 1.8 A. Assume the density of conduction electrons to be 9 × 10²⁸ m⁻³.

In the circuit shown in the figure, find the total resistance of the circuit and the current in the arm CD.

A battery of emf E and internal resistance, r, when connected with an external resistance of 12Ω produces a current of 0.5 A. When connected across a resistance of 25Ω, it produces a current of 0.25 A. Determine (i) the emf and (ii) the internal resistance of the cell.

A battery of emf 10 V and internal resistance 3 ohm is connected to a resistor. If the current in the circuit is 0.5 A, find : (i) the resistance of the resistor; (ii) the terminal voltage of the battery.

A cell of emf E and internal resistance r is connected to two external resistances R₁ and R₂ and a perfect ammeter. The current in the circuit is measured in four different situations : (i) without any external resistance in the circuit (ii) with resistance R1 only (iii) with R1 and R2 in series combination (iv) with R1 and R2 in parallel combination. The currents measured in the four cases are 0.42 A, 1.05 A, 1.4 A and 4.2 A, but not necessarily in that order. Identify the currents corresponding to the four cases mentioned above.

In the circuit shown in the figure, find the current through each resistor.