Science (English Medium) कक्षा १२ - CBSE Important Questions

A rectangular loop of wire of size 2.5 cm × 4 cm carries a steady current of 1 A. A straight wire carrying 2 A current is kept near the loop as shown. If the loop and the wire are coplanar, find the (i) torque acting on the loop and (ii) the magnitude and direction of the force on the loop due to the current carrying wire.

Calculate the value of the resistance R in the circuit shown in the figure so that the current in the circuit is 0.2 A. What would b the potential difference between points B and E?

Calculate the value of the resistance R in the circuit shown in the figure so that the current in the circuit is 0.2 A. What would b the potential difference between points A and B?

A magnetised needle of magnetic moment 4.8 × 10⁻² JT⁻¹ is placed at 30° with the direction of uniform magnetic field of magnitude 3 × 10⁻² T. Calculate the torque acting on the needle.

In the meter bridge experiment, balance point was observed at J with AJ = l.

(i) The values of R and X were doubled and then interchanged. What would be the new position of balance point?

(ii) If the galvanometer and battery are interchanged at the balance position, how will the alance point get affected?

In the given circuit, assuming point A to be at zero potential, use Kirchhoff’s rules to determine the potential at point B.

State the principle of the working of a moving coil galvanometer, giving its labeled diagram ?

Outline the necessary steps to convert a galvanometer of resistance RG into an ammeter of a given range ?

Using Ampere’s circuital law, obtain the expression for the magnetic field due to a long solenoid at a point inside the solenoid on its axis ?

In what respect is a toroid different from a solenoid? 

 Draw and compare the pattern of the magnetic field lines in the two cases ?

How is the magnetic field inside a given solenoid made strong?

A long straight wire of a circular cross-section of radius ‘a’ carries a steady current ‘I’. The current is uniformly distributed across the cross-section. Apply Ampere’s circuital law to calculate the magnetic field at a point ‘r’ in the region for (i) r < a and (ii) r > a.

State the underlying principle of working of a moving coil galvanometer. Write two reasons why a galvanometer can not be used as such to measure current in a given circuit. Name any two factors on which the current sensitivity of a galvanometer depends.

Derive the expression for force per unit length between two long straight parallel current carrying conductors. Hence define one ampere.

A square loop of side 'a' carrying a current I₂ is kept at distance x from an infinitely long straight wire carrying a current I₁ as shown in the figure. Obtain the expression for the resultant force acting on the loop. 

Explain the significance of a radial magnetic field when a current-carrying coil is kept in it. 

Answer the following question.
Two infinitely long straight wire A₁ and A₂ carrying currents I and 2I flowing in the same direction are kept' distance apart. Where should a third straight wire A₃ carrying current 1.5 I be placed between A₁ and A₂ so that it experiences no net force due to A₁ and A₂? Does the net force acting on A₃ depend on the current flowing through it?

Twelve wires each having a resistance of 3 Ω are connected to form a cubical network. A battery of 10 V and negligible internal resistance is connected across the diagonally opposite corners of this network. Determine its equivalent resistance and the current along each edge of the cube.

A planar loop of rectangular shape is moved within the region of a uniform magnetic field acting perpendicular to its plane. What is the direction and magnitude of the current induced in it?