Current Electricity · Physics · NEET

A uniform wire of diameter $$d$$ carries a current of $$100 \mathrm{~mA}$$ when the mean drift velocity of electrons in the wire is $$v$$. For a wire of diameter $$\frac{d}{2}$$ of the same material to carry a current of $$200 \mathrm{~mA}$$, the mean drift velocity of electrons in the wire is

A uniform metal wire of length $$l$$ has $$10 \Omega$$ resistance. Now this wire is stretched to a length $$2l$$ and then bent to form a perfect circle. The equivalent resistance across any arbitrary diameter of that circle is

The given circuit shows a uniform straight wire $$A B$$ of $$40 \mathrm{~cm}$$ length fixed at both ends. In order to get zero reading in the galvanometer $$G$$, the free end of $$J$$ is to be placed from $$B$$ at:

The terminal voltage of the battery, whose emf is $$10 \mathrm{~V}$$ and internal resistance $$1 \Omega$$, when connected through an external resistance of $$4 \Omega$$ as shown in the figure is:

A wire of length '$$l$$' and resistance $$100 \Omega$$ is divided into 10 equal parts. The first 5 parts are connected in series while the next 5 parts are connected in parallel. The two combinations are again connected in series. The resistance of this final combination is:

Two heaters $$A$$ and $$B$$ have power rating of $$1 \mathrm{~kW}$$ and $$2 \mathrm{~kW}$$, respectively. Those two are first connected in series and then in parallel to a fixed power source. The ratio of power outputs for these two cases is:

Choose the correct circuit which can achieve the bridge balance.

A certain wire $$\mathrm{A}$$ has resistance $$81 ~\Omega$$. The resistance of another wire $$\mathrm{B}$$ of same material and equal length but of diameter thrice the diameter of A will be :

A copper wire of radius $$1 \mathrm{~mm}$$ contains $$10^{22}$$ free electrons per cubic metre. The drift velocity for free electrons when $$10 \mathrm{~A}$$ current flows through the wire will be (Given, charge on electron $$=1.6 \times 10^{-19} \mathrm{C}$$ ) :

The emf of a cell having internal resistance $$1 \Omega$$ is balanced against a length of $$330 \mathrm{~cm}$$ on a potentiometer wire. When an external resistance of $$2 \Omega$$ is connected across the cell, the balancing length will be :

The magnitude and direction of the current in the following circuit is :-

If the galvanometer $$G$$ does not show any deflection in the circuit shown, the value of $$R$$ is given by:

Resistance of a carbon resistor determined from colour codes is $$(22000 \pm 5 \%) \Omega$$. The colour of third band must be :

The resistance of platinum wire at $$0^{\circ} \mathrm{C}$$ is $$2 ~\Omega$$ and $$6.8 ~\Omega$$ at $$80^{\circ} \mathrm{C}$$. The temperature coefficient of resistance of the wire is :

10 resistors, each of resistance $$\mathrm{R}$$ are connected in series to a battery of emf $$E$$ and negligible internal resistance. Then those are connected in parallel to the same battery, the current is increased $$n$$ times. The value of $$n$$ is :

The reciprocal of resistance is :

A cell of emf 4 V and internal resistance 0.5 $$\Omega$$ is connected to a 7.5 $$\Omega$$ external resistance. The terminal potential difference of the cell is

The equivalent resistance of the infinite network given below is :

The sliding contact C is at one fourth of the length of the potentiometer wire (AB) from A as shown in the circuit diagram. If the resistance of the wire AB is R₀, then the potential drop (V) across the resistor R is

Two resistors of resistance, 100 $$\Omega$$ and 200 $$\Omega$$ are connected in parallel in an electrical circuit. The ratio of the thermal energy developed in 100 $$\Omega$$ to that in 200 $$\Omega$$ in a given time is

A copper wire of length 10 m and radius $$\left( {{{{{10}^{ - 2}}} \over {\sqrt \pi }}} \right)$$ m has electrical resistance of 10 $$\Omega$$. The current density in the wire for an electric field strength of 10 (V/m) is

A wheatstone bridge is used to determine the value of unknown resistance X by adjusting the variable resistance Y as shown in the figure. For the most precise measurement of X, the resistance P and Q