Govt. Exams
The magnetic force on a current-carrying conductor is F = BIL sinθ, where θ is the angle between the current direction and the magnetic field. When θ = 90°, force is maximum (BIL), and when θ = 0°, force is zero.
Magnetic field lines always form closed loops and cannot exist in isolation. Unlike electric field lines which start from positive charges and end at negative charges, magnetic field lines have no beginning or end.
By Faraday's law, induced EMF = -dΦ/dt. Magnetic flux Φ = BA = πr²B. As B changes from 0 to B₀ in time t, EMF = πr²(B₀-0)/t = πr²B₀/t
Motional EMF = BLv (where L is perpendicular to both B and v)
A shunt (low resistance in parallel) diverts excess current, protecting the galvanometer coil
B = μ₀nI = μ₀(N/L)I = 4π × 10⁻⁷ × 1000 × 2 = 8π × 10⁻⁴ T
r ∝ 1/B. When B is doubled, r becomes r/2
Magnetic force F = qvB. Since both have same charge magnitude and velocity, forces are equal in magnitude (directions opposite due to opposite charges)
Parallel currents in same direction attract each other with force per unit length F/L = μ₀I₁I₂/(2πd)
Using Biot-Savart law for a circular loop, the magnetic field at center is B = μ₀I/(2R)
