CBSE Class 12 Physics Magnetic Effects of Electric Current Basic Problems

CBSE Class 12 Physics Magnetic Effects of Electric Current Basic Problems. Please refer to the examination notes which you can use for preparing and revising for exams. These notes will help you to revise the concepts quickly and get good marks.

1. A current I equal to 2 ampere circulates in a round thin wire loop of radius r = 100 mm. Find the magnetic induction
(a) at the centre of the loop
(b) at a point on the axis of the loop at a distance x = 100 mm from its centre

2. Find the magnetic induction at the point O if a wire carrying current I has the shape shown in figure (a, b). The radius of the curved part of the wire is R and the linear parts may be assumed to be very long.

3. A particle of mass 9 × 10^–31 kg and negative charge of 1.6 × 10^–19 coulomb is projected horizontally with a velocity of 10⁶ m/sec into a region between two infinite horizontal parallel plates of metal. The distance between the plates is 0.3 cm and the particle enters 0.1 cm below the top plate. The top and bottom plates are connected respectively to the positive and negative terminals of a 30 volt battery. Find the components of the velocity just before the particle hits one of the plates.

4. A non-relativistic proton beam passed without deviation through a region of space where there are mutually perpendicular uniform electric and magnetic fields with E = 120 kV/m and B = 50 mT. Then the beam strikes a ground target. Find the force with which the beam acts on the target if the beam current is equal to 0.8 mA.

5. Two long parallel wires of zero resistance are connected to each other by a battery of 1.0 V. The separation between the wires is 0.5 m. A metallic bar, which is perpendicular to the wires and of resistance 10Ω, moves on these wires when a magnetic field of 0.02 Tesla is acting perpendicular to the plane containing the bar and the wires. Find the steady state velocity of the bar. If the mass of the bar is 0.002 kg, find its velocity as a function of time.

6. A galvanometer having 30 divisions has a current sensitivity of 20 μA/ division. It has a resistance of 25 ohm. How will you convert in into an ammeter measuring upto 1 ampere? How will you now convert this ammeter into a voltmeter reading upto 1 volt?

7. Two straight infinitely long and thin parallel wires are spaced 0.1 m apart and carry a current of 10 ampere each. Find the magnetic field at a point distant 0.1 m from both wires in the two cases when the currents are in the
(a) same and (b) opposite directions.

8. In the Bohr model of hydrogen atom, the electron circulates around the nucleus in the path of radius 5.1 × 10^–11 m at a frequency of 6.8 × 10¹⁵ rev/s.
(a) Calculate the magnetic induction B at the centre of the orbit.
(b) What is the equivalent dipole moment?

9. The wire loop PQRSP formed by joining two semi-circular wires of radii R1 and R2 carries a current I as shown in Fig. What is the magnetic induction at the centre O and magnetic moment of the loop in cases (A) and (B)?

10. A loop of flexible conducting wire of length 0.5 m lies in a magnetic field of 1.0 Tesla perpendicular to the plane of the loop. Calculate the tension developed in the wire if the current is of 1.57 ampere.

11. A coil in the shape of an equilateral triangle of side 0.02 m is suspended from a vertex such that it is hanging in a vertical plane between the pole pieces of a permanent magnet producing a horizontal magnetic field of 5 × 10–2 T. Find the couple acting on the coil when a current of 0.1 ampere is passed through it and the magnetic field is parallel to its plane.

12. The magnetic field existing in a region is given by A 

    B=B₀(1+x/l)k'

square loop of edge l and carrying a current i, is placed with its edges parallel to the X – Y axes. Find the magnitude of the net magnetic force experienced by the loop

13. A narrow beam of singly charged carbon ions, moving at a constant velocity of 6.0 × 10⁴ m/s, is sent perpendicularly in a rectangular region having uniform magnetic field B = 0.5 T. It is found that two beams emerge from the field in the backward direction, the separations from the incident beam being 3.0 cm and 3.5 cm. Identify the isotopes present in the ion beam. Take the mass of an ion = A(1.6 × 10^–27) kg, where A is the mass number.

14. A battery is connected between two points A and B on the circumference of a uniform conducting ring of radius r and resistance R as shown in Fig. One of the arcs AB of the ring subtends an angle θ at the centre. What is the value of the magnetic field at the centre due to the current in the ring?

15. A solenoid of length 0.4 m and having 500 turns of wire carries a current of 3 ampere. A thin coil having 10 turns of wire and of radius 0.01 m carries a current of 0.4 ampere. Calculate the torque required to hold the coil in the middle of the solenoid with its axis perpendicular to the axis of the solenoid.

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