Current Electricity

The average current in the steady state registered by the ammeter in the circuit will be

The temperature dependence of resistances of Cu and undoped Si in the temperature range 300-400 K, is best described by :

A galvanometer having a coil resistance of 100 Ω gives a full scale deflection, when a current of 1 mA is passed through it. The value of the resistance, which can convert this galvanometer into ammeter giving a full scale deflection for a current of 10 A, is :

In the following 'I' refers to current and other symbols have their usual meaning. Choose the option that corresponds to the dimensions of electrical conductivity :

In the circuit shown, the resistance r is a variable resistance. If for r = fR, the heat generation in r is maximum then the value of f is :

A 50 Ω resistance is connected to a battery of 5 V. A galvanometer of resistance 100 Ω is to be used as an ammeter to measure current through the resistance, for this a resistance $r_s$ is connected to the galvanometer. Which of the following connections should be employed if the measured current is within 1% of the current without the ammeter in the circuit ?

The resistance of an electrical toaster has a temperature dependence given by $R(T)=R_0[1+\alpha(T-T_0)]$ in its range of operation. At $T_0=300$ K, R = 100 Ω and at T = 500 K, R = 120 Ω. The toaster is connected to a voltage source at 200 V and its temperature is raised at a constant rate from 300 to 500 K in 30 s. The total work done in raising the temperature is :

In an aluminum (Al) bar of square cross section, a square hole is drilled and is filled with iron (Fe) as shown in the figure. The electrical resistivities of Al and Fe are $2.7\times10^{-8}\ \Omega$ m and $1.0\times10^{-7}\ \Omega$ m, respectively. The electrical resistance between the two faces P and Q of the composite bar is

In the following circuit, the current through the resistor $R$ $(=2\ \Omega)$ is $I$ Amperes. The value of $I$ is

Consider two different metallic strips (1 and 2) of the same material. Their lengths are the same, widths are $w_1$ and $w_2$ and thicknesses are $d_1$ and $d_2$, respectively. Two points $K$ and $M$ are symmetrically located on the opposite faces parallel to the $x$-$y$ plane (see figure). $V_1$ and $V_2$ are the potential differences between $K$ and $M$ in strips 1 and 2, respectively. Then, for a given current $I$ flowing through them in a given magnetic field strength $B$, the correct statement(s) is(are)

Consider two different metallic strips (1 and 2) of same dimensions (length $l$, width $w$ and thickness $d$) with carrier densities $n_1$ and $n_2$, respectively. Strip 1 is placed in magnetic field $B_1$ and strip 2 is placed in magnetic field $B_2$, both along positive $y$-directions. Then $V_1$ and $V_2$ are the potential differences developed between $K$ and $M$ in strips 1 and 2, respectively. Assuming that the current $I$ is the same for both the strips, the correct option(s) is(are)

When 5V potential difference is applied across a wire of length 0.1 m, the drift speed of electrons is $2.5\times10^{-4}$ ms$^{-1}$. If the electron density in the wire is $8\times10^{28}$ m$^{-3}$, the resistivity of the material is close to :

In the circuit shown, the current in the 1Ω resistor is :

Suppose the drift velocity $v_d$ in a material varied with the applied electric field E as $v_d\propto\sqrt E$. Then V - I graph for a wire made of such a material is best given by :

A 10V battery with internal resistance 1Ω and a 15V battery with internal resistance 0.6Ω are connected in parallel to a voltmeter (see figure). The reading in the voltmeter will be close to :

In the electric network shown, when no current flows through the 4 Ω resistor in the arm EB, the potential difference between the points A and D will be :

The AC voltage across a resistance can be measured using a :

Heater of an electric kettle is made of a wire of length $L$ and diameter $d$. It takes 4 minutes to raise the temperature of 0.5 kg water by 40 K. This heater is replaced by a new heater having two wires of the same material, each of length $L$ and diameter $2d$. The way these wires are connected is given in the options. How much time in minutes will it take to raise the temperature of the same amount of water by 40 K?

Two ideal batteries of emf $V_1$ and $V_2$ and three resistances $R_1$, $R_2$ and $R_3$ are connected as shown in the figure. The current in resistance $R_2$ would be zero if

A galvanometer gives full scale deflection with 0.006 A current. By connecting it to a 4990 Ω resistance, it can be converted into a voltmeter of range 0-30 V. If connected to a $\dfrac{2n}{249}\ \Omega$ resistance, it becomes an ammeter of range 0-1.5 A. The value of $n$ is