Current Electricity Questions

A wire of resistance $R$ is cut into $8$ equal pieces. From these pieces two equivalent resistances are made by adding four of these together in parallel. Then these two sets are added in series. The net effective resistance of the combination is:

A constant voltage of $50\text{V}$ is maintained between the points A and B of the circuit shown in the figure. The current through the branch CD of the circuit is:

The current passing through the battery in the given circuit is:

A current of $2\text{A}$ flows through a $2\Omega$ resistor when connected across a battery. The same battery supplies a current of $0.5\text{A}$ when connected across a $9\Omega$ resistor. The internal resistance of the battery is:

If power dissipated in the $9\Omega$ resistor in the circuit shown is $36\text{Watt}$, the potential difference across the $2\Omega$ resistor is:

The rate of increase of thermo e.m.f. with temperature at the neutral temperature of a thermocouple:

The resistances of the four arms $P,Q,R,S$ in a Wheatstone bridge are $10\Omega ,30\Omega ,30\Omega ,90\Omega$ respectively. The e.m.f. is $7\text{V}$ and internal resistance is $5\Omega$. What is the current drawn from the cell?

A filament bulb $(500\text{W},100\text{V})$ is to be used in a $230\text{V}$ main supply. When a resistance $R$ is connected in series, the bulb works perfectly and consumes $500\text{W}$. The value of $R$ is:

The potential difference $(V_A-V_B)$ between points $A$ and $B$ in the given figure is:

An inductor $20\text{mH}$, a capacitor $50\mu \text{F}$ and a resistor $40\Omega$ are connected in series across a source of emf $V=10\sin 340t$. The power loss in A.C. circuit is:

The power dissipated in the circuit shown (two $10\Omega$ resistors in parallel connected to $R$ in series, $10\text{V}$ battery) is $30\text{Watts}$. The value of $R$ is:

A cell with emf $ϵ$ and internal resistance $r$ is connected to variable $R$. Plot of potential difference $V$ across $R$ vs $R$ is:

A ring is made of a wire having a resistance $R_0=12\Omega$. Find the points $A$ and $B$, as shown in the figure, at which a current carrying conductor should be connected so that the resistance $R$ of the sub circuit between these points is equal to $8/3\Omega$.

In the circuit shown the cells $A$ and $B$ have negligible resistances. For $V_A=12\text{V},R_1=500\Omega$ and $R=100\Omega$ the galvanometer ($G$) shows no deflection. The value of $V_B$ is:

If voltage across a bulb rated $220\text{Volt}-100\text{Watt}$ drops by $2.5\%$ of its rated value, the percentage of the rated value by which the power would decrease is:

A milli voltmeter of $25\text{mV}$ range is to be converted into an ammeter of $25\text{A}$ range. The value (in ohm) of necessary shunt will be:

A wire of resistance $4\Omega$ is stretched to twice its original length. The resistance of the stretched wire would be:

The internal resistance of a $2.1\text{V}$ cell which gives a current of $0.2\text{A}$ through a resistance of $10\Omega$ is:

A small signal voltage $V(t)=V_0\sin \omega t$ is applied across an ideal capacitor $C$:

Two cities are $150\text{km}$ apart. Electric power is sent from one city to another city through copper wires. The fall of potential per $\text{km}$ is $8\text{volt}$ and the average resistance per $\text{km}$ is $0.5\Omega$. The power loss in the wire is:

The resistance in the two arms of the meter bridge are $5\Omega$ and $R\Omega$, respectively. When the resistance $R$ is shunted with an equal resistance, the new balance point is at $1.6l_1$. The resistance '$R$ ', is:

A potentiometer circuit has been set up for finding the internal resistance of a given cell. When the resistance, $R$, connected across the given cell, has values of (i) infinity and (ii) $9.5\Omega$, the 'balancing lengths' are found to be $3\text{m}$ and $2.85\text{m}$, respectively. The value of internal resistance of the cell is:

In an ammeter $0.2\%$ of main current passes through the galvanometer. If resistance of galvanometer is $G$, the resistance of ammeter will be:

A potentiometer wire of length $L$ and a resistance $r$ are connected in series with a battery of e.m.f. $E_0$ and a resistance $r_1$. An unknown e.m.f. $E$ is balanced at a length $l$ of the potentiometer wire. The e.m.f. $E$ will be given by:

Two metal wires of identical dimensions are connected in series. If ${\sigma }_1$ and ${\sigma }_2$ are the conductivities of the metal wires respectively, the effective conductivity of the combination is:

A series R-C circuit is connected to an alternating voltage source. Consider two situations:(i) When capacitor is air filled.(ii) When capacitor is mica filled.Current through resistor is $i$ and voltage across capacitor is $V$ then:

A circuit contains an ammeter, a battery of $30\text{V}$ and a resistance $40.8\Omega$ all connected in series. If the ammeter has a coil of resistance $480\Omega$ and a shunt of $20\Omega$, the reading in the ammeter will be:

A potentiometer wire is $100\text{cm}$ long and a constant potential difference is maintained across it. Two cells are connected in series first to support one another and then in opposite direction. The balance points are obtained at $50\text{cm}$ and $10\text{cm}$ from the positive end of the wire in the two cases. The ratio of emf’s is:

The charge flowing through a resistance $R$ varies with time $t$ as $Q=at-b{t}^2$ where $a$ and $b$ are positive constants. The total heat produced in $R$ is:

A wire of a certain material is stretched slowly by ten per cent. Its new resistance and specific resistance become respectively:

For ensuring dissipation of same energy in all three resistors ($R_1,R_2,R_3$) connected as shown in figure, their values must be related as:

In producing chlorine through electrolysis $100\text{W}$ power at $125\text{V}$ is being consumed. How much chlorine per min is liberated? ECE of chlorine is $0.367\times 10^{-6}\text{kg/C}$:

In the circuit shown, if a conducting wire is connected between points A and B, the current in this wire will: (All resistance given in ohms)

Two cells having the same emf, are connected in series through an external resistance $R$. Cells have internal resistance $r_1$ and $r_2$ respectively. When the circuit is closed, the potential difference across the first cell is zero. The value of $R$ is:

The power dissipated across the $8\Omega$ resistor in the circuit shown here is $2\text{W}$. The power dissipated in watt units across the $3\Omega$ resistor is :(Assume a circuit where the $8\Omega$ and $24\Omega$ resistors are in parallel, and their combination is in series with a $3\Omega$ resistor)

Kirchhoff’s first and second laws for electrical circuits are consequences of:

The total power dissipated in watts in the circuit shown here is:

The resistance of an ammeter is $13\Omega$ and its scale is graduated for a current up to $100\text{A}$. After an additional shunt has been connected to this ammeter it becomes possible to measure currents up to $750\text{A}$ by this meter. The value of shunt resistance is:

A steady current of $1.5\text{A}$ flows through a copper voltmeter for $10\text{min}$. If the electrochemical equivalent of copper is $30\times 10^{-5}{\text{gC}}^{-1}$, the mass of copper deposited on the electrode will be:

Three resistances $P,Q,R$ each of $2\Omega$ and an unknown resistance $S$ form the four arms of a Wheatstone’s bridge circuit. When a resistance of $6\Omega$ is connected in parallel to $S$ the bridge gets balanced. What is the value of $S$?

A cell can be balanced against $110\text{cm}$ and $100\text{cm}$ of potentiometer wire, respectively with and without being short circuited through a resistance of $10\Omega$. Its internal resistance is:

In the circuit shown, if $V_A=0$, what is the potential at point $B$?

In a circuit, the current through a $4\Omega$ resistor is $1\text{A}$ when the points $P$ and $M$ are connected to a d.c. voltage source. The potential difference between the points $M$ and $N$ is:

An electric kettle takes $4\text{A}$ current at $220\text{V}$. How much time will it take to boil $1\text{kg}$ of water from temperature $20^{\circ }\text{C}$? The temperature of boiling water is $100^{\circ }\text{C}$.

A current of $3\text{A}$ flows through the $2\Omega$ resistor shown in the circuit. The power dissipated in the $5\Omega$ resistor is:

A galvanometer of resistance $50\Omega$ is connected to a battery of $3\text{V}$ along with a resistance of $2950\Omega$ in series. A full scale deflection of $30$ divisions is obtained in the galvanometer. In order to reduce this deflection to $20$ divisions, the resistance in series should be:

Consider an electric circuit consisting of two batteries with emfs ${ϵ}_1,{ϵ}_2$ and internal resistances $r_1,r_2$ connected in parallel with an external resistance $R$. If $i_1$ and $i_2$ are currents through the respective branches, which of the following Kirchhoff equations is correct?

A wire of resistance $12\Omega /\text{m}$ is bent to form a complete circle of radius $10\text{cm}$. The resistance between its two diametrically opposite points, $A$ and $B$, is:

A galvanometer having a coil resistance of $60\Omega$ shows full scale deflection when a current of $1.0\text{A}$ passes through it. It can be converted into an ammeter to read currents up to $5.0\text{A}$ by:

A student measures the terminal potential difference ($V$) of a cell (of emf $ϵ$ and internal resistance $r$) as a function of the current ($I$) flowing through it. The slope and intercept of the graph between $V$ and $I$ are respectively:

The mean free path of electrons in a metal is $4\times 10^{-8}\text{m}$. The electric field which can give on an average $2\text{eV}$ energy to an electron in the metal will be in units of $\text{V/m}$:

A galvanometer of resistance $G$ is shunted by a resistance $S$ ohm. To keep the main current in the circuit unchanged, the resistance to be put in series with the galvanometer is:

A thermocouple of negligible resistance produces an $e.m.f.$ of $40\mu {\text{V/}}^{\circ }\text{C}$ in the linear range. A galvanometer of resistance $10\Omega$ with sensitivity $1\mu \text{A/div}$ is used. The smallest temperature difference detectable is: