Current electricity practice · Mixed difficulty

The mobility of free electrons (charge $=\mathrm{e}$, mass $=\mathrm{m}$ and relaxation time $=\tau$ ) in a metal is proportional to

If a copper wire is stretched to make it $0.1 \%$ longer, the percentage change in its resistance is

The production of $e.m.f.$ by maintaining a difference of temperature between the two junctions of two different metals is known as

An electrical cable having a resistance of $0.2\,\,\mathrm{\Omega }$ delivers $10\,\,\mathrm{k}\,\mathrm{W}$ at $200\,\,V\,\mathrm{D}\,\mathrm{C}$ to a factory. What is the efficiency of transmission

A certain piece of copper is to be shaped into a conductor of minimum resistance. Its length and diameter should be respectively

Twelve wires of equal resistance $R$ are connected to form a cube. The effective resistance between two opposite diagonal ends will be

If current is passed through $\mathrm{Sb}-\mathrm{Bi}$ thermocouple then

An immersion heater is rated $\mathrm{418}\,\,\mathrm{W}$. It should heat a litre of water from $10\,^\circ C$ to $30\,^\circ C$ in nearly

It is possible that any some constant value of emf, but the potential difference between the plates is zero?

A wire is stretched so as to change its diameter by $\mathrm{0}\mathrm{.25}\,\,\mathrm{\% }$. The percentage change in resistance is

Potentiometer measures the potential difference more accurately than a voltmeter because

Which one of the following physical quantities does NOT affect the resistance of a cylindrical resistor?

Two bulbs when connected in parallel to a source take $\mathrm{100 W}$ each. The total power consumed when they are connected in series with the same source is
 

The current density (number of free electrons per ${\mathrm{m}^3}$) in metallic conductor is of the order of

Potential gradient is defined as

Ohm's law is valid if

Which of the following is the unit of mobility of a electron in a conductor?

Kirchoff’s second law for the analysis of circuit is based on

Given a current carrying wire of non-uniform cross section. Which of the following quantity or quantities are constant throughout the length of the wire?

Which one of the following statements concerning Ohm's law is true?

A metallic resistor is connected across a battery. If the number of collisions of the free electrons with the lattice is some how decreased in the resistor (for example by cooling it), the current will

When the current $i$ is flowing a conductor, the drift velocity is $v$. If $2i$ current is flowed through the same metal but having double the area of cross-section, then the drift velocity will be

Statement-1: The value of temperature coefficient of resistance is positive for metals.
Statement-2: The temperature coefficient of resistance for insulator is also positive.

A generator of emf 100 V has an internal resistance of 0.04 ohm. If its terminal voltage is 95 V, then the current in the circuit is

If temperature is decreased, then relaxation time of electrons in metals will

The resistance of hot tungsten filament is about $\mathrm{10}\,\,\mathrm{times}$ the cold resistance. What will be the resistance of $\mathrm{100}\,\,\mathrm{W}$ and $\mathrm{200}\,\,\mathrm{V}$ lamp, when not in use?

Assertion: Resistivity of metals decreases with decrease in temperature but have some finite value as the temperature approaches absolute zero.
Reason: The residual resistivity near absolute zero is caused primarily by the collision of electrons with impurities and imperfections in the metal.

A wire of resistance $4 \Omega$ is used to wind a coil of radius $7 \mathrm{~cm}$. The wire has a diameter of $1.4 \mathrm{~mm}$ and the specific resistance of its material is $2 \times 10^{-7} \Omega m$. Find the number of turns in the coil.

Assertion: There is no current in the metals in the absence of electric field.

Reason: Motion of free electrons are randomly.

Assertion: Terminal potential difference of a cell is always less than its emf.
Reason: Potential drop due to internal resistance of cell increases the terminal potential difference.