The area of cross-section of a copper wire is $4 \times 10^{-7} \mathrm{~m}^2$ and the electrons per cubic metre in copper is $8 \times 10^{28}$. If the wire carries a current of 6.4 A , then the drift velocity of the electrons ( $\mathrm{in} 10^{-3} \mathrm{~ms}^{-1}$ ) is

In the given circuit, the internal resistance of the cell is zero. If $i_1$ and $i_2$ are the readings of the ammeter when the key $(K)$ is opened and closed respectively, then $i_1: i_2=$

In a meter bridge, the null point is located at 20 cm from left end of the wire when resistances $R$ and $S$ are connected in the left and right gaps respectively. If the resistance $S$ is shunted with $60 \Omega$ resistance, the null point shifted by 5 cm , then the values of $R$ and $S$ are respectively

The readings of the voltmeter and ammeter in the circuit shown in the diagram are respectively

When two identical batteries of internal resistance $1 \Omega$ each are connected in series across a resistor $R$, the rate of heat produced in $R$ is $P_1$. When the same batteries are connected in parallel across $R$, the rate of heat produced is $P_2$. If $P_1=2.25 P_2$, then the value of $R$ is

The potential difference across a conducting wire of length 20 cm is 30 V . If the electron mobility is $2 \times 10^{-6} \mathrm{~m}^2 \mathrm{~V}^{-1} \mathrm{~s}^{-1}$, then the drift velocity of the electrons is

A maximum current of 0.5 mA can pass through a galvanometer of resistance $15 \Omega$. The resistance to be connected in series to the galvanometer to convert it into a voltmeter of range $0-10 \mathrm{~V}$ is

A part of a circuit is shown in the figure. The ratio of the potential differences between the points $A$ and $C$ and the points $D$ and $E$ is

A wire of resistance ' $R$ ' is bent in the form of a circular loop. Two points on the circle seperated by a quarter circumference are connected to a battery of emf ' $E$ ' and negligible internal resistance. The heat generated in the wire per second is

When a wire is connected in the left gap of a metre bridge, the balancing point is at 40 cm from the left end of the bridge wire. If the wire in the left gap is stretched so that its length is doubled and again connected in the same gap, then the balancing point from the left end of the bridge wire is

The length and area of cross-section of a copper wire are respectively 30 m and $6 \times 10^{-7} \mathrm{~m}^2$. If the resistivity of copper is $1.7 \times 10^{-8} \Omega \mathrm{~m}$, then the resistance of the wire is

If current of 80 A is passing through a straight conductor of length 10 m , then the total momentum of electrons in the conductor is

(mass of electron $=9.1 \times 10^{-31} \mathrm{~kg}$ and charge of electron $=1.6 \times 10^{-19} \mathrm{C}$ )

Charge ' $Q$ ' (in coulomb) flowing through a conductor in terms of time ' $t$ ' (in second) is given by the equation $Q=3 t^2+t$. The current in the conductor at time $t=3 \mathrm{~s}$ is

In a metal, the charge carrier density is $9.1 \times 10^{28} \mathrm{~m}^{-3}$ and its electrical conductivity is $6.4 \times 10^7 \mathrm{~S} \mathrm{~m}^{-1}$. When an electric field of $10 \mathrm{NC}^{-1}$ is applied to the metal, then the average time between two successive collisions of electrons in the metal is

(Mass of electron $=9.1 \times 10^{-31} \mathrm{~kg}$, charge of electron $=1.6 \times 10^{-19} \mathrm{C}$ )

A straight wire of resistance $18 \Omega$ is bent in the form of an equilateral triangular loop. The effective resistance between any two vertices of the triangle is

The power dissipated by a uniform wire of resistance $100 \Omega$ when a potential difference of 120 V is applied across its ends is

A wire of resistance $100 \Omega$ is stretched, so that its length increases by $20 \%$. The stretched wire is then bent in the form of a rectangle whose length and breadth are in the ratio $3: 2$. The effective resistance between the ends of any diagonal of the rectangle is

In a potentiometer experiment, when two cells of emfs $E_1$ and $E_2\left(E_2>E_1\right)$ are connected in series, the balancing length is 160 cm . If one of the cells is reversed, the balancing length decreases by $75 \%$. If $E_1=1.2 \mathrm{~V}$, then $E_2=$

In the circuit shown in the figure, neglecting the source resistance, the voltmeter and ammeter readings respectively are

If $E_1=4 \mathrm{~V}$ and $E_2=12 \mathrm{~V}$, the current in the circuit and potential difference between the points $P$ and $Q$ respectively are

In the given circuit values of $I_1, I_2, I_3$ are respectively

The resistance of wire at $0^{\circ} \mathrm{C}$ is $20 \Omega$. If the temperature coefficient of the resistance is $5 \times 10^{-3}{ }^{\circ} \mathrm{C}^{-1}$. The temperature at which the resistance will be double of that at $0^{\circ} \mathrm{C}$ is

The electrons take $40 \times 10^3$ s to dirift from one end of a metal wire of length 2 m to its other end. The area of cross-section of the wire is $4 \mathrm{~mm}^2$ and it is carrying a current of 1.6 A. The number density of free electrons in the metal wire is

The current 'I' in the circuit shown in the figure is

Current density in a cylindrical wire of radius $R$ varies with radial distance as $\beta\left(r+r_0\right)^2$. The current through the section of the wire shown in the figure is

A cell can supply currents of 1 A and 0.5 A via resistances of $2.5 \Omega$ and $10 \Omega$, respectively. The internal resistance of the cell is

The conductivity of a conductor decreases with temperature because, on heating

Five current carrying conductors meet at a point P. What is the magnitude and direction of the current in the fifth conductor?

In a potentiometer of 10 wires, the balance point is obtained on the 6th wire. To shift the balance point to 8th wire, we should

The length of germanium rod is $0.925 \mathrm{~cm}$ and its area of cross-section is $1 \mathrm{~mm}^2$. If for germanium $n_i=2.5 \times 10^{19} \mathrm{~m}^{-3}, \propto_n=0.19 \mathrm{~m}^2 / \mathrm{V}-\mathrm{s}, \propto_e=0.39 \mathrm{~m}^2 / \mathrm{V}$-s, then the resistance of the rod is

A cell of emf 1.8 V gives a current of 17 A when directly connected to an ammeter of resistance 0.06 $\Omega$. Internal resistance of the cell is