Magnetic Materials
Magnetic Materials
- The magnetic susceptibility of a paramagnetic salt is \(\chi\) at 300 K. Its susceptibility at 200 K will be Answer: D. 1.5chi Curie's law: chi∝1/T⇒chi'=chi×300/200=1.5chi . 1
- The flux rule is the terminology that Feynman used to refer to the law relating magnetic flux to emf. Modern applications of Faraday’s law of induction : Electric generators and motors Dynamos in vehicles Transformers Induction furnaces (indu... 1
- Which property of soft iron makes it useful for preparing electromagnet? An electromagnet should become magnetic when a current is passed through its coil but should lose its magnetism once the current is switched... 1
- What should be retentivity and coercivity of permanent magnet? A permanent magnet should have a large zero-field magnetization and should need a very large reverse field to demagnetize. In other words, i... 1
- What does the hysteresis loop represents? A magnetic hysteresis loop is a closed curve obtained by plotting the magnetic flux density B of a ferromagnetic material against the corres... 1
- Explain one application of electromagnet. Applications of an electromagnet: Electromagnets are used in electric bells, loud speakers and circuit breakers. Large electromagnets are us... 1
- When a plate of magnetic material of size 10 cm × 0.5 cm × 0.2 cm (length , breadth and thickness respectively) Answer: B ≈ 0.635\ T Volume of the plate: V = 10 × 0.5 × 0.2 = 1\ mathrmcm³ = 1×10⁻⁶\ mathrmm³ Magnetisation (magnetic moment per unit volum... 1
- A rod of magnetic material of cross section 0.25 cm2 is located in 4000 Am-1 magnetising field Data: A = 0.25 cm² = 25 × 10⁻⁶ m², H = 4000 A∙m⁻¹, Φ = 25 × 10⁻⁶ Wb Magnetic induction is B = φ/A=frac25 × 10⁻⁶25 × 10⁻⁶ = 1 Wb/m² (a) B = µ... 1
- The work done for rotating a magnet with magnetic dipole momentm, through 90° from its magnetic meridian is n Data : θ₀ = 0°, θ₁ = 90°, θ₂ = 60°, W₁ = nW₂ The work done by an external agent to rotate the magnet from θ₀ to θ is W = MB (cos θ₀ – cos θ)... 1
- An electron in an atom is revolving round the nucleus in a circular orbit of radius 5.3 × 10-11 m, with a speed Data: r = 5.3 × 10⁻¹¹ m, v = 2 × 10⁶ m/s, e = 1.6 × 10⁻¹⁹ C, m_e = 9.1 × 10⁻³¹ kg The orbital magnetic moment of the electron is M₀ = 1/2 ev... 1
- A paramagnetic gas has 2.0 × 1026 atoms/m with atomic magnetic dipole moment of 1.5 × 10-23 A m2 each. Data: N/V = 2.0 × 10²⁶ atoms/m³, μ = 1.5 × 10⁻²³ Am2, T = 27 + 273 = 300 K, B = 3T, k^B = 1.38 × 10⁻²³ J/K, 1 eV = 1.6 × 10⁻¹⁹ J (a) The max... 1
- A magnetic needle placed in uniform magnetic field has magnetic moment of 2 × 10-2 A m2, and moment of inertia Data: M = 2 × 10⁻² A∙m², I = 7.2 × 10⁻⁷ kg∙m², T = 6/10 = 0.6 S T = 2π √(I/M B) The magnitude of the magnetic field is B = frac4 π² IM T² =... 1
- A short bar magnet is placed in an external magnetic field of 700 guass. When its axis makes an angle of 30° Data : B = 700 gauss = 0.07 tesla, θ = 30°, τ = 0.014 N∙m τ = MB sin θ The magnetic moment of the magnet is M = τ/B sin θ=frac(0.014)(0.07)(... 1
- Classify the following atoms as diamagnetic or paramagnetic. H, O, Zn, Fe, F, Ar, He Atoms Electronic configuration No. of Electrons Diamagnetic/Paramagnetic H 1s¹„ 1 Diamagnetic 0 1s²2s²2p⁴ 8 Paramagnetic Zn 1s²2s²2p⁶3s²3p⁶3... 2