CBSE Class 12 · 2012 · Current ElectricityVery Short Answer

An ammeter and a voltmeter are connected in series to a battery, their readings being $A$ and $V$ respectively. If a resistor is now connected in parallel with the voltmeter, then:

A galvanometer shows full-scale deflection for a current $I_g$. With a shunt $S_1$ it becomes an ammeter of range $(0\text{–}I)$; with a shunt $S_2$ its range becomes $(0\text{–}2I)$. Then $\frac{S_1}{S_2}$ is:

(i) Define the 'temperature coefficient of resistance' of a metal.
(ii) Show the variation of the resistivity of copper with a rise in temperature.
(iii) The resistance of a wire is $10\Omega$ at $27^{\circ }\text{C}$. Find its resistance at $-3^{\circ }\text{C}$, given the temperatu …

A current of $0.8\text{A}$ flows in a conductor of $40\Omega$ for 1 minute. The heat produced in the conductor will be:

A cell of EMF $E$ is connected across an external resistance $R$. When a current $I$ is drawn from the cell, the potential difference across its electrodes drops to $V$. The internal resistance $r$ of the cell is:

Define current density and relaxation time. Derive an expression for the resistivity of a conductor in terms of the number density of charge carriers and the relaxation time.