ISC Class 12 Current Electricity — practice questions
46 free MCQs with worked solutions. Tap any question for the answer + explanation, or practice them all in the app.
Practice ISC Class 12 Current Electricity in the app →The electric current across a cross-section of a conductor is defined as the net charge passing per unit time.A conductor carries a steady current when a charge of 30 C passes through a given cross-section in 1.5 minutesIn a solid metallic conductor with no external electric field applied, the average velocity of the free electrAccording to Ohm's law, the resistance R of a conductor is best described by which statement?Two identical conducting slabs, each of resistance R, are joined end to end so the total length doubles while A uniform conducting slab is cut lengthwise into two equal halves, each having half the original cross-sectionThe resistivity $\rho$ of a conductor, appearing in $R = \rho l / A$, depends onThe relation between the electric field E inside a conductor and the current density j, written in terms of coThe current density j flowing through a conductor of cross-sectional area A carrying current I (with current nIn the free-electron model, the drift velocity acquired by electrons in a steady field E (with $\tau$ the relaWhy do conduction electrons in a metal acquire a steady average drift velocity even though the applied electriA current is established almost the instant a circuit is switched on, even though the electron drift speed is A copper wire of cross-sectional area $1.0 \times 10^{-7}\ \text{m}^2$ carries a current of 1.5 A. The free-elFor conduction electrons in copper at room temperature, how does the drift speed typically compare with the raThe conductivity of a metal in the free-electron model is $ igma = ne^2\tau/m$. The mobility $\mu$ of the charMaterials are classified as conductors, semiconductors and insulators by resistivity. Metals fall in which ranHow does the resistivity of a typical semiconductor change as its temperature is increased?Resistivity of a metallic conductor varies with temperature as $\rho_T = \rho_0[1 + \alpha(T - T_0)]$. The temAlloys such as Nichrome, Manganin and Constantan are preferred for wire-bound standard resistors becauseA nichrome heating element has resistance 75.3 $\Omega$ at 27.0 °C. Connected to a 230 V supply it draws a steA platinum resistance thermometer reads 5 $\Omega$ at the ice point and 5.23 $\Omega$ at the steam point. In aThe power dissipated as heat in a resistor R carrying current I with voltage V across it can be written asA power P is to be delivered to a device through transmission cables of fixed resistance $R_c$, at a line voltA heater rated to dissipate power P is run from a fixed supply. If its resistance R is halved (voltage unchangThe electromotive force (emf) $\varepsilon$ of a cell is best described asA cell of emf $\varepsilon$ and internal resistance r drives a current I through an external resistor. The terA cell of emf $\varepsilon$ and internal resistance r is connected to an external resistance R. The current inA car storage battery has emf 12 V and internal resistance 0.4 $\Omega$. The maximum current that can be drawnA battery of emf 10 V and internal resistance 3 $\Omega$ is connected to a resistor and the circuit current isTwo cells of emfs $\varepsilon_1$ and $\varepsilon_2$ with internal resistances $r_1$ and $r_2$ are connected Two cells of emfs $\varepsilon_1$, $\varepsilon_2$ and internal resistances $r_1$, $r_2$ are connected in paraFor two cells in parallel, the equivalent emf $\varepsilon_{eq}$ and equivalent internal resistance $r_{eq}$ sTwo identical cells each of emf 1.5 V and internal resistance 0.5 $\Omega$ are connected in parallel (like terKirchhoff's junction rule, that the sum of currents entering a junction equals the sum leaving it, is a directKirchhoff's loop rule states that the algebraic sum of changes in potential around any closed loop is zero. ThA 10 V battery of negligible internal resistance is connected across diagonally opposite corners of a cubical For the cubical network of 12 one-ohm resistors driven by a 10 V battery (equivalent resistance 5/6 $\Omega$),In a balanced Wheatstone bridge with resistors $R_1, R_2, R_3, R_4$ (galvanometer across the B-D diagonal), thIn a Wheatstone bridge the unknown resistance is placed in the fourth arm. Known resistances $R_1$ and $R_2$ aA Wheatstone bridge has arms AB = 100 $\Omega$, BC = 10 $\Omega$, CD = 5 $\Omega$, DA = 60 $\Omega$. Is the brCurrent through an area of cross-section is treated as a scalar quantity in this chapter even though it is shoThe statement "$V = IR$ is itself the statement of Ohm's law" is, according to the text, incorrect. The correcA wire of length 15 m and uniform cross-section $6.0 \times 10^{-7}\ \text{m}^2$ has a measured resistance of A heating element has resistance 100 $\Omega$ at 27.0 °C. Its temperature coefficient of resistance is $1.70 \The number density of free electrons in a copper wire is $8.5 \times 10^{28}\ \text{m}^{-3}$. The wire is 3.0 A storage battery of emf 8.0 V and internal resistance 0.5 $\Omega$ is charged by a 120 V dc supply through a