Magnetic Effects of Current and Magnetism
Topics
- Biot-Savart law, field of circular loop
- Ampere's law: straight wire and solenoid
- Force on moving charge in magnetic and electric fields
- Force on current-carrying conductor, force between parallel currents
- Torque on current loop, moving coil galvanometer, conversion to ammeter and voltmeter
- Current loop and bar magnet as magnetic dipole, field along axis and equator
- Torque on magnetic dipole in uniform field
- Para-, dia- and ferromagnetism, effect of temperature
Chapter tests
See all →Top questions
See all →- A 2 amp current is flowing through two different small circular copper coils having radii ratio 1:2. The ratio of their respective magnetic moments will be Answer: 1. 1:4 Key idea: the magnetic moment of a current loop is M=IA=Iπ r² . The current is the same (2 A), so M∝ r² : M₁/M₂=(r₁/r₂)²=(1/2... 1
- An electron (mass 9×10^-31 kg and charge 1.6×10^-19C) moving with speed c/100 (c = speed of light) is injected into a magnetic field B of magnitude 9×10^-4 T perpendicular to its direction of motion. We wish to apply an uniform electric field E toget… Answer: 2. vec E is perpendicular to vec B and its magnitude is 27×10² V m ⁻¹ Key idea: for the electron to go undeflected, the electric for... 1
- An iron bar of length L has magnetic moment M. It is bent at the middle of its length such that the two arms make an angle 60^° with each other. The magnetic moment of this new magnet is: Answer: 3. M/2 Key idea: Magnetic moment = pole strength × distance between the poles. Bending changes this distance, not the pole strength.... 1
- A tightly wound 100 turns coil of radius 10 cm carries a current of 7 A. The magnitude of the magnetic field at the centre of the coil is (Take permeability of free space as 4π×10^-7 SI units): Answer: 4. 4.4 mT Key idea: Field at the centre of a circular coil of N turns: B=μ₀NI/2R . B=frac4π×10⁻⁷×100×72×0.1=frac8.8×10⁻⁴0.2≈4.4×10⁻³... 1
- Match List-I with List-II.List-I (Material): A. Diamagnetic; B. Ferromagnetic; C. Paramagnetic; D. Non-magneticList-II (Susceptibility ()): I. =0; II. 0>≥-1; III. 1; IV. 0<<ε (a small positive number)Choose the correct answer from the options given b… Answer: 2. A-II, B-III, C-IV, D-I Key idea: The sign and size of magnetic susceptibility chi identify the type of material. Diamagnetic: chi... 1
- In a uniform magnetic field of 0.049 T, a magnetic needle performs 20 complete oscillations in 5 seconds as shown. The moment of inertia of the needle is 9.8×10^-6 kg m^2. If the magnitude of magnetic moment of the needle is x×10^-5 Am^2; then the va… Answer: 1. 1280 π² Key idea: A magnetic needle in a field oscillates like a torsional pendulum: T=2π√(I/MB) . Period T=5/20=0.25 s. Squaring... 1