Current Electricity — JEE Main PYQs

A circuit to verify Ohm's law uses ammeter and voltmeter in series or parallel connected correctly to the resistor. In the circuit:

A galvanometer of resistance G is converted into a voltmeter of range $0-$ IV by connecting a resistance ${\mathrm{R}}_1$ in series with it. The additional resistance that should be connected in series with ${\mathrm{R}}_1$ to increase the range of the voltmeter to …

An electrical power line, having a total resistance of $2\Omega$, delivers 1 kW at 220 V. The efficiency of the transmission line is approximately:

For the given input voltage waveform ${\mathrm{V}}_{\text{in }}(\mathrm{t})$, the output voltage waveform ${\mathrm{V}}_0(\mathrm{t})$, across the capacitor is correctly depicted by:

A battery of 3.0 V is connected to a resistor dissipating 0.5 W of power. If the terminal voltage of the battery is 2.5 V, the power dissipated within the internal resistance is:

The value of current $i_1$ flowing from A to C in the circuit diagram is:

Four resistance $40\Omega ,60\Omega ,90\Omega$, and $110\Omega$ make the arms of a quadrilateral ABCD. Across AC is a battery of emf 40 V and internal resistance negligible. The potential difference across BD in V is ____

A $200\Omega$ resistor has a certain color code. If one replaces the red color by green in the code, the new resistance will be:

For the circuit shown, with ${\mathrm{R}}_1=1.0\Omega ,{\mathrm{R}}_2=2.0\Omega ,{\mathrm{E}}_1=2\mathrm{V}$ and ${\mathrm{E}}_2={\mathrm{E}}_3=4\mathrm{V}$, the potential difference between the points ' $a$ ' and ' $b$ ' is approximately (in V ):

In the circuit shown, a four wire potentiometer is made of a 400 cm long wire, which extends between $A$ and $B$. The resistance per unit length of the potentiometer wire is $r=0.01\Omega /\mathrm{cm}$. If an ideal voltmeter is connected as shown with jockey J at 50 cm from e …

A cell of internal resistance $r$ drives current through an external resistance $R$. The power delivered by the cell to the external resistance will be maximum when:

In the figure shown, what is the current (in Ampere) drawn from the battery? You are given

A moving coil galvanometer has resistance $50\Omega$ and it indicates full deflection at 4 mA current. A voltmeter is made using this galvanometer and a $5\mathrm{k}\Omega$ resistance. The maximum voltage, that can be measured using this voltamenter, will be close to:

A wire of resistance R is bent to form a square ABCD as shown in the figure. The effective resistance between $E$ and $C$ is: ( $E$ is mid-point of arm $CD$ )

A potentiometer wire AB having length L and resistance 12 r is joined to a cell D of emf $\epsilon$ and internal resistance r. A cell C having emf $\epsilon /2$ and internal resistance $3r$ is connected. The length AJ at which the galvanometer as shown in figure shows no …

A uniform metallic wire has a resistance of $18\Omega$ and is bent into an equilateral triangle. Then, the resistance between any two vertices of the triangle is:

In the given circuit the cells have zero internal resistance. The currents (in Amperes) passing through resistance ${\mathrm{R}}_1$ and ${\mathrm{R}}_2$ respectively, are:

A 2 W carbon resistor is color coded with green, black, red and brown respectively. The maximum current which can be passed through this resistor is:

A galvanometer having a resistance of $20\Omega$ and 30 divisions on both sides has figure of merit 0.005 ampere /division. The resistance that should be connected in series such that it can be used as a voltmeter upto 15 volt is:

In the experimental setup of metre bridge shown in the figure, the null point is obtained at a distance of 40 cm from A . If a $10\Omega$ resistor is connected in series with ${\mathrm{R}}_1$, the null point shifts by 10 cm . The resistance that should be connected in parallel w …

The circuit shown below contains two ideal diodes, each with a forward resistance of $50\Omega$. If the battery voltage is 6 V , the current through the $100\Omega$ resistance (in Amperes) is:

In the circuit shown, the potential difference between $A$ and $B$ is:

The resistive network shown below is connected to a D.C. source of 16 V. The power consumed by the network is 4 Watt. The value of $R$ is:

A galvanometer of resistance $100\Omega$ has 50 divisions on its scale and has sensitivity of $20\mu \mathrm{A}/$ division. It is to be converted to a voltmeter with three ranges, of $0-2\mathrm{V},0-10\mathrm{V}$ and $0-20\mathrm{V}$. The appropriate circuit to do so …

To verify Ohm's law, a student connects the voltmeter across the battery as, shown in the figure. The measured voltage is plotted as a function of the current, and the following graph is obtained:

If ${\mathrm{V}}_0$ is almost zero, identify the correct statement:

Space between two concentric conducting spheres of radii $a$ and $b(b>a)$ is filled with a medium of resistivity $\rho$. The resistance between the two spheres will be

The figure represents a voltage regulator circuit using a Zener diode. The breakdown voltage of the Zener diode is 6 V and the load resistance is ${\mathrm{R}}_{\mathrm{L}}=4\mathrm{k}\Omega$. The series resistance of the circuit is ${\mathrm{R}}_{\mathrm{i}}=1\mathrm{k}\Omega$. …

Two equal resistances when connected in series to a battery, consume electric power of 60 W . If these resistances are now connected in parallel combination to the same battery, the electric power consumed will be.

The resistance of the meter bridge AB in given figure is $4\Omega$. With a cell of emf $\epsilon =0.5\mathrm{V}$ and rheostat resistance ${\mathrm{R}}_{\mathrm{h}}=2\Omega$ the null point is obtained at some point J . When the cell is replaced by another one of emf …

In a Wheatstone bridge (see figure) Resistance $P$ and $Q$ are approximately equal. When $\mathrm{R}=400\Omega$, the bridge is balanced. On interchanging P and Q , the value of R , for balance is $405\Omega$. The value of X is close to:

An ideal battery of 4 V and resistance R are connected in series in the primary circuit of a potentiometer of length 1 m and resistance $5\Omega$. The value of R, to give a difference of 5 mV across 10 cm of potentiometer wire, is:

In a meter bridge, the wire of length 1 m has a nonuniform cross-section such that, the variation $\frac{\mathrm{dR}}{\mathrm{d}\ell }$ of its resistance R with length $\ell$ is $\frac{\mathrm{dR}}{\mathrm{d}\ell }\propto \frac{1}{\sqrt{\ell }}$. Two equal resistances are connect …

Two electric bulbs, rated at $(25\mathrm{W},220\mathrm{V})$ and $(100\mathrm{W},220\mathrm{V})$, are connected in series across a 220 V voltage source. If the 25 W and 100 W bulbs draw powers ${\mathrm{P}}_1$ and ${\mathrm{P}}_2$ respectively, then:

The galvanometer deflection, when key ${\mathrm{K}}_1$ is closed but ${\mathrm{K}}_2$ is open, equals ${\theta }_0$ (see figure). On closing $K_2$ also and adjusting ${\mathrm{R}}_2$ to $5\Omega$, the deflection in galvanometer becomes $\frac{{\theta }_0}{5}$. The …

One kg of water, at $20^{\circ }\mathrm{C}$, is heated in an electric kettle whose heating element has a mean (temperature averaged) resistance of $20\Omega$. The rms voltage in the mains is 200 V . Ignoring heat loss from the kettle, time taken for water to evaporate fully, is …

A moving coil galvanometer, having a resistance G, produces full scale deflection when a current ${\mathrm{I}}_{\mathrm{g}}$ flows through it. This galvanometer can be converted into (i) an ammeter of range 0 to ${\mathrm{I}}_0$ (${\mathrm{I}}_0>{\mathrm{I}}_{\mathrm{g}}$) by connectin …

A galvanometer, whose resistance is 50 ohm, has 25 divisions in it. When a current of $4\times 10^{-4}\mathrm{A}$ passes through it, its needle (pointer) deflects by one division. To use this galvanometer as a voltmeter of range 2.5 V, it should be connected to a resistance …

In the given circuit diagram, the currents, $I_1=-0.3\mathrm{A},I_4=0.8\mathrm{A}$ and $I_5=0.4\mathrm{A}$, are flowing as shown. The currents $I_2,I_3$ and $I_6$, respectively are:

The charge on a capacitor plate in a circuit, as a function of time, is shown in the figure :

What is the value of current at $t=4s$ ?

A metal wire of resistance $3\Omega$ is elongated to make a uniform wire of double its previous length. The new wire is now bent and the ends joined to make a circle. If two points on this circle make an angle $60^{\circ }$ at the centre, the equivalent resistance between these t …

The resistance of a galvanometer is 50 ohm and the maximum current which can be passed through it is 0.002 A. What resistance must be connected to it in order to convert it into an ammeter of range $0-0.5\mathrm{A}$?

In a conductor, if the number of conduction electrons per unit volume is $8.5\times 10^{28}{\mathrm{m}}^{-3}$ and mean free time is 25fs (femto second), its approximate resistivity is: $({\mathrm{m}}_{\mathrm{e}}=9.1\times 10^{-31}\mathrm{kg})$

In the given circuit the internal resistance of the 18 V cell is negligible. If ${\mathrm{R}}_1=400\Omega ,{\mathrm{R}}_3=100\Omega$ and ${\mathrm{R}}_4=500\Omega$ and the reading of an ideal voltmeter across ${\mathrm{R}}_4$ is 5 V , then the value of ${\mathrm{R}}_2$ will b …

A resistance is shown in the figure. Its value and tolerance are given respectively by:

Drift speed of electrons, when 1.5 A of current flows in a copper wire of cross section $5{\text{ mm}}^2$, is v. If the electron density in copper is $9\times 10^{28}/{\text{m}}^3$ the value of v in mm/s is close to (Take charge of electron to be $=1.6\times 10^{-19}$ C)

Mobility of electron in a semiconductor is defined as the ratio of their drift velocity to the applied electric field. If, for an $n$-type semiconductor, the density of electrons is $10^{19}{m}^{-3}$ and their mobility is $1.6{\mathrm{m}}^2/(\mathrm{V}.\mathrm{s})$ then …

A copper wire is stretched to make it $0.5\%$ longer. The percentage change in its electric resistance if its volume remains unchanged is

When the switch S , in the circuit shown, is closed, then the value of current i will be

In an experiment, the resistance of a material is plotted as a function of temperature (in some range). As shown in the figure, it is a straight line. One may conclude that:

In the given circuit, an ideal voltmeter connected across the $10\Omega$ resistance reads 2 V . The internal resistance r, of each cell is: