Q8: Wire coil parallel to changing magnetic field
A 100-turn wire coil has a resistance of 400 Ω and a cross-sectional area of 0.01 m^2. The coil is placed in a magnetic field directed parallel to the axis of the coil. If the field changes at a rate of -0.4 T//s, what is the current induced in the coil? The flux ø_B = BA => (∆ø_B)/(∆t) = (∆B)/(∆t)A (∆ø_B)/(∆t) = (-0.4 T//s)(0.01 m^2) = -4.0 × 10^-3 Wb//s The emf induced in 100-loop coil: ℰ = -N(∆ø_B)/(∆t) = -(100)(-4.0 × 10^-3 Wb//s) = 0.4 V I = ℰ /R = (0.4 V)/(400 Ω) = 1 × 10^-3 A