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#conducting rod

3 public questions tagged with this topic.

A conducting rod moves perpendicular to a uniform magnetic field with constant velocity. What is true about the induced

**Self-induction** emf induced in coil due to change in its own current, e = -L dI/dt, L self-inductance (H), L = μ₀ N² A / l for solenoid, N turns, A area (m²), l length (m), μ₀=4π×10⁻⁷ H/m. For solenoid 650 turns/m means n=650, A=0.014 m², L = μ₀ n² A l? Actually per unit length? For length l, N=n l, L= μ₀ n² A l, if l=1 m, L=4π×10⁻⁷×650²×0.014=7.43×10⁻³ H, dI/dt=(3-6)/0.25=-12 A/s, e= -L×(-12)=0.089 V. The induced emf ( ε = B l v ) remains constant because the velocity, magnetic field, and rod length are constant, leading to a steady flux change rate.

Ref: NCERT > Physics Book > Electromagnetic Induction > Self-Induction and Self-Inductance

A conducting rod is moved perpendicular to a uniform magnetic field. The emf induced across its ends depends on which of

**Field decreasing to zero** induces emf trying to maintain field, current direction such that its field adds to original. For 150 turns area 0.06 m² B 0.14 T to zero in 0.3 s, e=150×0.06×0.14/0.3=4.2 V, as earlier, showing linear dependence on N, A, ΔB/Δt. The motional emf is given by ε = B l v , where B is the magnetic field strength, l is the length of the rod, and v is its velocity, all of which are critical factors. Using Φ = B A cosθ, e = -N dΦ/dt = -N A dB/dt = B l v = N B A ω sinωt,

Ref: NCERT > Physics Book > Electromagnetic Induction > Induced EMF Due to Change in Magnetic Field

A conducting rod moves parallel to its length in a uniform magnetic field. Why is no emf induced across its ends?

**Rectangular loop moving out of field** emf e = B l v, l side perpendicular to motion cutting field lines, e constant while partially in field, zero when fully out, duration t = (side parallel to motion)/v. For 0.38×0.55 m loop B=0.65 T v=0.7 m/s along shorter side 0.38 m, l=0.55 m (side cutting), e=0.65×0.55×0.7=0.25 V, lasts t=0.38/0.7=0.54 s. Motional emf requires the rod to move perpendicular to the magnetic field to cut flux lines. Moving parallel to its length does not change the flux through any area, so no emf is induced. Using Φ = B A cosθ, e = -N dΦ/dt = -N

Ref: NCERT > Physics Book > Electromagnetic Induction > Motional EMF - Rod and Rectangular Loop