A voltmeter of resistance $400 \Omega$ is used to measure the emf of a cell with an internal resistance of $4 \Omega$. The error in the measurement of emf of the cell is

When two wires are connected in the two gaps of a meter bridge, the balancing length is 50 cm . When the wire in the right gap is stretched to double its lengt ${ }^{-}$ and again connected in the same gap, then the new balancing length from the left. end of the bridge wiu :

The resistance of a wire is $2.5 \Omega$ at a temperature 373 K . If the temperature coeffficient of resistance of the material of the wire is $3.6 \times 10^{-3} \mathrm{~K}^{-1}$, its resistance at a temperatrue 273 K is nearly.

When two identical resistors are connected in series to an ideal cell, the current through each resistor is 2 A . If the resistors are connected in parallel to the cell, the current through each resistor is

A conductor of length 1.5 m and area of cross-section $3 \times 10^{-5} \mathrm{~m}^2$ has electrical resistance of $15 \Omega$.

The current density in the conductor for an electric field of $21 \mathrm{Vm}^{-1}$ is

The relation between the current $i$ (in ampere) in a conductor and the time $t$ (in second) is $i=12 t+9 t^2$. The charge passing through the conductor between the times $t=2 \mathrm{~s}$ and $t=10 \mathrm{~s}$ is

The potential difference between the ends of a straight conductor of length 20 cm is 16 V . If the drift speed of the electrons is $2.4 \times 10^{-4} \mathrm{~ms}^{-1}$, the electron mobility in $\mathrm{m}^2 \mathrm{~V}^{-1} \mathrm{~s}^{-1}$ is

The potential difference $V$ across the filament of the bulb shown in the given Wheatstone bridge varies as $V=i(2 i+1)$, where $i$ is the current in ampere through the filament of the bulb. The emf of the battery $V_a$, so that the bridge become balanced is

When the temperature of a wire is increased from 303 K to 356 K , the resistance of the wire increases by $10 \%$. The temperature coefficient of resistance of the material of the wire is

Three resistors of resistances $10 \Omega, 20 \Omega$ and $30 \Omega$ are connected as shown in the figure. If the points $A, B$ and $C$ are at potentials $10 \mathrm{~V}, 6 \mathrm{~V}$ and 5 V respectively, then the ratio of the magnitudes of the currents through $10 \Omega$ and $30 \Omega$ resistors is

When a potentiometer is connected between the points $A$ and $B$ as shown in the circuit, balance point is obtained at 64 cm . When it is connected between $A$ and $C$, the balance point is 8 cm . If the potentiometer is connected between $B$ and $C$ the balance point will be

In the given part of a circuit, the potential at point $B$ is zero. Then, the potentials at $A$ and $C$ respectively, are