Current Electricity

Resistance of the wire is measured as 2 $\Omega$ and 3 $\Omega$ at 10°C and 30°C respectively. Temperature co-efficient of resistance of the material of the wire is :

A coil is placed in a time varying magnetic field. If the number of turns in the coil were to be halved and the radius of wire doubled, the electrical power dissipated due to the current induced in the coil would be :

(Assume the coil to be short circuited.)

All resistances in figure are 1 $\Omega$ each. The value of current 'I' is $\dfrac a5$ A. The value of a is ______.

Two coils require 20 minutes and 60 minutes respectively to produce same amount of heat energy when connected separately to the same source. If they are connected in parallel arrangement to the same source; the time required to produce same amount of heat by the combination of coils, will be ______ min.

The variation of applied potential and current flowing through a given wire is shown in figure. The length of wire is 31.4 cm. The diameter of wire is measured as 2.4 cm. The resistivity of the given wire is measured as $x\times10^{-3}$ $\Omega$ cm. The value of $x$ is ______.

[Take $\pi=3.14$]

For the network shown below, the value of $V_B-V_A$ is ______ V.

The combination of two identical cells, whether connected in series or parallel combination provides the same current through an external resistance of 2$\Omega$. The value of internal resistance of each cell is

Two resistors are connected in series across a battery as shown in figure. If a voltmeter of resistance 2000 $\Omega$ is used to measure the potential difference across 500 $\Omega$ resister, the reading of the voltmeter will be ______ V

An electric cable of copper has just one wire of radius 9 mm. Its resistance is 14 $\Omega$. If this single copper wire of the cable is replaced by seven identical well insulated copper wires each of radius 3 mm connected in parallel, then the new resistance of the combination will be :

The circuit diagram of potentiometer used to measure the internal resistance of a cell (E) is shown in figure. The key 'K' is kept closed so as to send constant current through potentiometer wire. When key '$K_1$' is kept open the null point is found to be at 120 cm on the potentiometer wire. When the key '$K_1$' is closed the null point is shifted at 80 cm at the potentiometre wire. The internal resistance of the given cell is ______ $\Omega$.

In the given figure, the value of $V_o$ will be ______ V.

Eight copper wire of length $l$ and diameter d are joined in parallel to form a single composite conductor of resistance R. If a single copper wire of length $2l$ have the same resistance (R) then its diameter will be ______ d.

A current of 15 mA flows in the circuit as shown in figure. The value of potential difference between the points A and B will be :

In a potentiometer arrangement, a cell of emf 1.20 V gives a balance point at 36 cm length of wire. This cell is now replaced by another cell of emf 1.80 V. The difference in balancing length of potentiometer wire in above conditions will be ______ cm.

Two ideal diodes are connected in the network as shown is figure. The equivalent resistance between A and B is ______ $\Omega$.

The current I in the given circuit will be :

Resistances are connected in a meter bridge circuit as shown in the figure. The balancing length $l_1$ is 40 cm. Now an unknown resistance $x$ is connected in series with P and new balancing length is found to be 80 cm measured from the same end. Then the value of $x$ will be ______ $\Omega$.

A battery of 6 V is connected to the circuit as shown below. The current I drawn from the battery is :

In a coil of resistance 8 Ω, the magnetic flux due to an external magnetic field varies with time as $\phi=\dfrac23\left(9-t^2\right)$. The value of total heat produced in the coil, till the flux becomes zero, will be ______ J.

A potentiometer wire of length 300 cm is connected in series with a resistance 780 Ω and a standard cell of emf 4 V. A constant current flows through potentiometer wire. The length of the null point for cell of emf 20 mV is found to be 60 cm. The resistance of the potentiometer wire is ______ Ω.