What is relaxation time ? Derive an expression for resistivity of a wire in terms of number density of free electrons and relaxation time.
Using the concept of drift velocity of charge carriers in a conductor, deduce the relationship between current density and resistivity of the conductor.
How does the random motion of free electrons in a conductor get affected when a potential difference is applied across its ends ?
The plot of the variation of potential difference across a combination of three identical cells in series, versus current is shown below. What is the emf and internal resistance of each cell ?
A cell of emf 4 V and internal resistance 1 W is connected to a d.c. source of 10 V through a resistor of 5 W. Calculate the terminal voltage across the cell during charging.
A network of resistors is connected to a 16 V battery with internal resistance of 1 Ω, as shown in the following figure. Compute the equivalent resistance of the network.
Draw a graph to show the variation of resistance of a metal wire as a function of its diameter keeping its length and material constant.
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.
The figure shows two sinusoidal curves representing oscillating supply voltage and current in an ac circuit.
Using the concept of drift velocity of charge carriers in a conductor, deduce the relationship between current density and resistivity of the conductor.
An electric dipole is placed in a uniform electric field with its dipole moment parallel to the field. Find
(i) the work done in turning the dipole till its dipole moment points in the direction opposite to .
(ii) the orientation of the dipole for which the torque acting on it becomes maximum.
Two cells of emf and have internal resistance and . Deduce an expression for equivalent emf of their parallel combination.
A lamp is connected in series with a capacitor. Predict your observation for dc and ac connections. What happens in each if the capacitance of the capacitor is reduced ?
Write two properties of equipotential surfaces. Depict equipotential surfaces due to an isolated point charge. Why do the equipotential surfaces get closer as the distance between the equipotential surfaces and the source charge decreases ?