Current electricity practice · Medium

An immersion heater with electrical resistance $7\,\,\mathrm{\Omega }$ is immersed in $\mathrm{0}\mathrm{.1}\,\,\mathrm{kg}$ of water at $20\,{\,^0}\mathrm{C}$ for $\mathrm{3}\,\,\mathrm{min}$. If the flow of current is $\mathrm{4}\,\,\mathrm{A}$, what is the final temperature of the water in ideal conditions? ${\left( {\mathrm{Specific heat }\,\mathrm{capacity}\,\mathrm{ of }\,\mathrm{water} = 4.2\,\, \times \,{{10}^3}\,\,\mathrm{Jkg}} \right)^{ - 1}}{\mathrm{K}^{ - 1}}$

In a meter bridge, null point is $20 \mathrm{~cm}$. When the known resistance $\mathrm{R}$ is shunted by $10 \Omega$ resistance, null point is found to be shifted by $10 \mathrm{~cm}$. The value of unknown resistance $\mathrm{X}$ is.

When a current passes through the junction of two different metals, evolution or absorption of heat at the junction is known as

One junction of thermocouple is at $0\,{\,^0}\mathrm{C}$ and the other is at $T\,{\,^0}\mathrm{C}$. The thermo emf (in volts) is given by $E = 20\,\, \times \,\,{10^{ - 6}}\,\,T - 0.02\,\, \times \,\,{10^{ - 6}}\,\,{T^2}$ The maximum value of $E$ is

A capacitor of capacity $C$ is charged to a potential difference $V$ and another capacitor of capacity $2 \mathrm{C}$ is charged to a potential difference $4 \mathrm{~V}$. The charging batteries are disconnected and the two capacitors are connected with reverse polarity (i.e. positive plate of first capacitor is connected to negative plate of second capacitor). The heat produced during the redistribution of charge between the capacitors will be

For comparing the e.m.f.'s of two cells with a potentiometer, a standard cell is used to develop a potential gradient along the wires. Which of the following possibilities would make the experiment unsuccessful

If in a voltaic cell, $\mathrm{5}\,\,\mathrm{g}$ of zinc is consumed, we will get how many ampere hour (given that $\mathrm{ECE}$ of zinc is $3.38\,\, \times \,\,{10^{ - 7}}\,\,\mathrm{kg}{\mathrm{C}^{ - 1}}$)

Three unequal resistors in parallel are equivalent to a resistance $1\,\,\mathrm{\Omega }$. If two of them are in the ratio $\mathrm{1:2}$ and if no resistance value is fractional, the largest of the three resistance in ohm is

Under what condition will the strength of current in a wire of resistance $R$ be the same for connection is n series or in parallel of $n$ identical cells each of the internal resistance $r$, when

A current passes through a wire of unequal cross-sectional area. The one that does not depend on cross- section among the following is

As the temperature rises the resistance offered by metals

Two identical cells send the same current in $3\,\,\Omega$resistance, whether connected in series or in parallel. The internal resistance on the cell should be

What is the volume of hydrogen liberated at $\mathrm{NTP}$ by the amount of charge which liberates $\mathrm{0}\mathrm{.3175}\,\mathrm{ g}$ of copper?

The commercial unit of electrical energy is kilowatt-hour (kWh), which is equal to

Which one of the following devices is nonohmic?

Two identical heaters of $\mathrm{220}\,\,\mathrm{V , 1000 W}$ are placed in parallel with each other across $\mathrm{220}\,\,\mathrm{V}$ line, then the combined power is

In comparing e.m.f. of two cells with the help of a potentiometer,if the balance point is to be shifted to a longer length of the wire, then this can be done by

If one cell is connected wrongly in a series combination of four cells each of e.m.f $1.5 {~V}$ and internal resistance of $0.5 \Omega$, then the equivalent internal resistance of the combination is

Which of the following are true, when the cells are connected in series?

Assertion: When a straight wire is bent to form L-shape, its resistance increases.
Reason: Electrons take longer time to travel along bent-wire as compared to travel along a straight wire.

Kirchhoff's junction rule is a reflection of :

In parallel combination of $n$ cells, we obtain

Statement-I: In a balanced Wheatstone bridge if cell and galvanometer arms are interchanged, reading of the galvanometer remains unchanged.
Statement-II: For a balanced Wheatstone bridge, current detected by galvanometer is zero.

In meter bridge arrangement, resistances $x$ and $y$ are used in 2 gaps of bridge. Null point is at distance of $25 \mathrm{~cm}$ from one of the end wire $(y>x)$. If resistance of $2 x$ is used instead of $x$ then calculate distance of null point from same end of wire.

The electrical conductivity of a metal is

A student has $\mathrm{10}\,\,\mathrm{resistors}$ of resistance $'r'$. The minimum resistance made by him from given resistors is

Four wires made of same material have different lengths and radii. The wire having more resistance in the following case is

Assertion: Conductivity of a metals is much higher than that of an electrolyte at room temperature.
Reason: Free electron density in metals is much larger than the density of ions in electrolytes and also free electrons have greater mobility than ions.

To deposit one gm equivalent of an element at an electrode, the quantity of electricity needed is

For mobile charge carries of mass $m$, the mobility is :