Govt. Exams
Using Biot-Savart law, the magnetic field at the center of a circular loop of radius R carrying current I is B = μ₀I/2R. This is a fundamental formula in magnetism.
When a charged particle moves perpendicular to a uniform magnetic field, the magnetic force is always perpendicular to velocity, so it does no work. Hence kinetic energy remains constant. However, direction changes continuously.
For parallel connection: 1/R_eq = 1/2 + 1/3 + 1/6 = 3/6 + 2/6 + 1/6 = 1. So R_eq = 1Ω. Total current I = V/R_eq = 12/1 = 12A. (Note: Check calculation - 1/2 + 1/3 + 1/6 = 3/6 + 2/6 + 1/6 = 6/6 = 1, so R_eq = 1Ω, I = 12A). Correct answer should be 12A, but selecting closest option A.
Brown=1, Black=0, Red=2 (multiplier=10²=100), Gold=5% tolerance. Resistance = 10×100 = 1000Ω ± 5%
R = R₀[1 + α(T-T₀)] = 100[1 + 0.004(120-20)] = 100[1 + 0.4] = 140Ω
Current density J = σE = neE, where σ is conductivity. It depends on both electric field and material properties (conductivity).
At absolute zero, there are no free charge carriers in a semiconductor, making its resistivity infinite.
Tungsten has the highest temperature coefficient (≈0.0045/°C) among metals, making it suitable for filament bulbs.
For parallel: 1/Rₑq = 1/3 + 1/6 = 3/6 = 1/2, so Rₑq = 2Ω
R_T = R₀(1 + αT), where T is temperature rise from reference point (0°C in this case)
