Current electricity practice · Mixed difficulty

The resistance of a conductor does not depend on

Water boils in an electric kettle in $15\,\,minutes$ after switching on. If the length of the heating wire is decreased to $\mathrm{2/3}$ of its initial value, then the same amount of water will boil with the same supply voltage in

The thermo emf $\mathrm{E}$ in volts of a certain thermocouple is found to vary with temperature difference $\theta$ in ${ }^{\circ} \mathrm{C}$ between the two junctions according to the relation $\mathrm{E}=30 \theta-\frac{\theta^2}{15}$, then the neutral temperature of thermocouple is

Which of the following acts as a circuit protecting device?

One junction of a certain thermo-couple is at a fixed temperature ${T_r}$ and the other junction is at temperature $T$. The thermo electric force for this is expressed by
$E = K\left( {T - {T_r}} \right)\,\,[\,{T_0}\,\, + \,\,\frac{1}{2}\left( {{T^2} + T_r^2)\,} \right]$
At temperature $T = {T_0}/2$ the thermoelectric power is

Electrical conductivity of insulators is

The charge flown through a resistance $\mathrm{R}$ in time $\mathrm{t}$ varies with time according to $\mathrm{Q}=\mathrm{at}-\mathrm{bt}^2$. The total heat produced in $\mathrm{R}$ by the time current becomes zero is :

If the temperature of cold junction of thermocouple is lowered, then the neutral temperature

In potentiometer a balance point is obtained, when:-

If a wire is stitched to four times its length then the specific resistance of the wire will:

Consider four conducting materials copper, tungsten, mercury and aluminium with resistivity ${\rho _C},{\rho _T},{\rho _M}$ and ${\rho _A},$ respectively. Then,

Incandescent bulbs are designed by keeping in mind that the resistance of their filament increases with the increase in temperature. If at room temperature, $\mathrm{100 }\,\mathrm{W,}\,\mathrm{ 60 }\,\mathrm{W}\,\mathrm{ and }\,\mathrm{40}\,\mathrm{ W}$ bulbs have filament resistances ${R_{100}},\,\,{R_{60}}\,\,\mathrm{and}\,\,{R_{40}}$, respectively, the relation between these resistances is

On passing the current in water voltmeter, hydrogen

The resultant resistance value of three resistors each of $r ~\Omega$ are connected in series is $x$. When given three resistances are connected in parallel, the resultant value is

Statement I : Specific resistance depends on nature of material and independent of temperature of the material.

Statement II : A wire of resistance $6 \Omega$ is drawn out so that its new length is four times its original length. The resistance of the new wire is $\mathbf{4 8 \Omega} \Omega$.

Statement III: Drift velocity is the average constant velocity acquired by free electrons inside a metal by the application of an electric field which results in current.

Which of the following is correct?

A $12\,\,HP$ motor has to be operated $8\,\,h/day$. How much will it cost at the rate of $50\,\,paise/kWh$h in $10\,\,days\,\,?$

The conductivity of a superconductor is

Mobility of free electrons in a conductor is :

A $25\,\,W,\,\,220\,\,V$ bulb and a $100\,\,W,\,\,220\,\,V$ bulb are connected in parallel across a $440\,\,V$ line

An electric lamp is marked $60\,\,W,\,\,230\,\,V$. The cost of a $1\,\,kWh$ of energy is $Rs.\,\,1.25$. The cost of using this lamp $8\,\,hrs$ a day for $\mathrm{30 }\,\mathrm{days}$ is

The specific resistance of a conducting wire depends upon

A current I flows through a potential difference $V$ in an electrical circuit containing a resistance $R$. The product of $V$ and $I$, i.e., VI may be understood as

Assertion: EMF of battery decreases with time.
Reason: Internal resistance increases with time.

A resistor develops $400 \mathrm{~J}$ of heat in $10 \mathrm{~s}$ when a current of $2 \mathrm{~A}$ is passed through it. The resistance and the energy developed in $10 \mathrm{~s}$. If the current is doubled is

Ohm's law defines