Current electricity practice · Medium

A cell of emf $2 \mathrm{~V}$ and internal resistance $0.1 ~\Omega$ is connected to a $3.9 ~\Omega$ external resistance. What will be the p.d. across the terminals of the cell ?

Consider a wire of length $4 \mathrm{~m}$ and cross-sectional area 1 $\mathrm{mm}^2$ carrying a current of $2 \mathrm{~A}$. If each cubic metre of the material contains $10^{29}$ free electrons, find the average time taken by an electron to cross the length of the wire.

Consider the following two statements $A$ and $B$, and identify the correct choice out of given answers

A. Thermo $e.\mathrm{m}\mathrm{.f}.$ is minimum at neutral temperature of a thermocouple

B. When two junctions made of two different metallic wires are maintained at different temperatures, an electric current is generated in the circuit

An electric bulb is rated $\mathrm{220}\,\,\mathrm{V - 100}\,\,\mathrm{W}$. The power consumed by it when operated on $\mathrm{110}\,\,\mathrm{V}$ will be

Mobility of free electron in a current carrying conductor is proportional to

Piece of Aluminium and Silicon both are heated from $-10^{\circ} {C}$ to $40^{\circ} {C}$. The resistivity of

Internal resistance of a cell is independent of

A parallel-plate capacitor has plate area $20 \mathrm{~cm}^2$, plate separation $1.0 \mathrm{~mm}$ and a dielectric slab of dielectric constant $5.0$ filling up the space between the plates. This capacitor is joined to a battery of emf $6.0 \mathrm{~V}$ through a $100 \mathrm{k} \Omega$ resistor. Find the energy of the capacitor $8.9 \mu \mathrm{s}$ after the connections are made.

Metals have

Point out the right statements about the validity of Kirchhoff's junction rule

A wire of resistance $R$ is elongated $n -$ fold to make a new uniform wire. The resistance of new wire

The speed at which the current travels, in a conductor, is nearly

The Avogadro’s number is $6\,\, \times \,\,{10^{23}}$ per gm mole and electronic charge is $1.6\,\, \times \,\,{10^{ - 19}}\,\,C$. The Faraday’s number is

Which of the following statements is correct

The electric resistance of a certain wire of iron is $R.$. If its length and radius are both doubled, then

Total emf produced in a thermocouple does not depend on

In a metallic conductor, drift velocity $v_d$ is related with electric field $E$ as

A battery of e.m.f. $₹$ ', and internal resistance ' $r$ ', gives a current of $0.5 \mathrm{~A}$ with an external resistor of $12 \mathrm{~ohm}$ and a current of $0.25 \mathrm{~A}$ with an external resistor of $25 \mathrm{~ohm}$. Calculate (i) internal resistance of the cell and (ii) emf of the cell.

Resistance of a wire is $10 \Omega$. Its length is increased $50 \%$ by stretching it. Calculate its new resistance.

The resistivity of a wire

The masses of the wires of copper are in the ratio 1 : 2 : 3 and their lengths are in the ratio 3 : 2 : 1. The ratio of their electrical resistance

Ampere hour is the unit of

A parallel-plate capacitor with plate area $20 \mathrm{~cm}^2$ and plate separation $1.0 \mathrm{~mm}$ is connected to a battery. The resistance of the circuit is $10 \mathrm{k} \Omega$. Find the time constant of the circuit.

Assertion: A potentiometer is preferred over that of a voltmeter for measurement of emf of a cell.
Reason: Potentiometer does not draw any current from the cell.

In a current carrying metallic conductor, current density $\vec{J}$ and drift velocity $\overrightarrow{v_d}$ will be such that

When two identical batteries of internal resistance $1\,\,\mathrm{\Omega }$ each are connected in series across a resistor $R$, the rate of heat produced in $R$ is ${J_1}$. When the same batteries are connected $\mathrm{I}$ parallel across $R$, the rate is ${J_2}$. If ${J_1} = 2.25\,\,{J_2}$ then the value of $R$ in $\mathrm{\Omega }$ is

A cathode emits $1.8 \times {10^{14}}$ electrons per second. When heated when 400 V is applied to anode all the emitted electrons reach the anode. The charge on electron is $1.6 \times {10^{ - 19}}C$. The maximum anode current is

A potentiometer is an ideal device of measuring potential difference because

To get the maximum current from a parallel combination of $n$ identical cells each of internal resistance $r$ and external resistance $R$, when

Two bulbs of $\mathrm{250}\,\,\mathrm{V}$ and $\mathrm{100}\,\,\mathrm{W}$ are first connected in series and then in parallel with a supply of $\mathrm{250}\,\,\mathrm{V}$. Total power in each of the case will be respectively