Class 12 Physics Magnetic Field Notes and Important Questions
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Important Questions
Obtain an expression for magnetic field strength at the centre of current carrying circular coil using Biot-Savart's law.
A slice of indium antimonide 2.5 mm thick carries a current of 150 mA. A magnetic field of flux density 0.5 T, correctly applied, produces a maximum Hall voltage of 8.75 mV between the edges of the slice. Calculate the number of free charge carriers per unit volume assuming they each have a charge of −1.6 × 10⁻¹⁹ C.
Derive an expression for the force exerted per unit length between two parallel current carrying conductors if currents are flowing in the same direction. Hence, define one ampere current.
A student wants to measure the magnetic flux density between the poles of two weak bar magnets mounted on a steel yoke as shown in the figure. The magnitude of the flux density is between 0.02T and 0.04T.
Define Magnetic flux density.
One way of measuring the magnetic flux density could be the use of a Hall probe. Suggest one reason why Hall probe is not a suitable instrument to measure the magnetic flux density for the arrangement shown in the below figure.
A circular coil of radius R is carrying a constant current I. Find an expression for magnetic field at point P, which is at a distance x on its axial line.
Why is Hall voltage much more measurable in semiconductors than metals? Explain
Draw magnetic field lines around the two parallel current carrying conductors in which currents are in opposite direction.
Two long parallel conductors are placed 0.1 m apart and carry currents of 3 A and 2 A, respectively, in the same direction. Calculate the force per unit length experienced by each conductor due to the other.
(μ₀ = 4π × 10⁻⁷ Hm⁻¹)
Biot-Savart law gives the magnitude of magnetic field produced by a current carrying conductor.
i) State Biot-Savart law.
ii) Use Biot-Savart law to calculate the magnetic field of a circular current carrying coil at its centre.
iii) Also determine the direction of the magnetic field in this case.
The magnetic field intensity at the center of a circular coil of radius R and carrying current I is
μ₀I/R
μ₀I/2R
μ₀I/2πR
2μ₀I/R
Obtain an expression for the magnetic field intensity at any point due to a straight current carrying conductor using Ampere's circuital law.
A wire of length 0.5 m carrying a current of 2 A is placed in a uniform magnetic field of strength 0.4 T. Find the maximum and minimum force experienced by it.
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Past Question Analysis
Historical exam-pattern data from past NEB question papers — not a prediction of future questions.
7
Question Items
8
Total Marks
4
Papers Appeared In
| Year | Question Items | Marks |
|---|---|---|
| 2082 | 3 | 1 |
| 2081 | 1 | — |
| 2080 | 1 | 5 |
| 2078 | 2 | 2 |
Also appears in 2 model questions (not counted above — model sets aren't actual NEB exam history).
Magnetic Field introduces the relationship between electric current and magnetism. It covers magnetic force, magnetic flux, Biot-Savart law, Ampere's law, Hall effect, current-carrying conductors, coils and galvanometers.
This page covers Magnetic Field, chapter 16 of 25 in the Class 12 Physics syllabus set by the National Examination Board (NEB). 10 important questions for this chapter are available, each with a full solution.
For numerical and derivation-based chapters like this one, working through past NEB questions is usually more useful than re-reading notes alone — try solving each important question above before checking the solution, then compare your working step by step.