A very long solenoid of inner radius 4.25 cm creates an oscillating magnetic field B of the form B = B m a x cos ( ω t ) For this solenoid, B max = 0.00275 T and ω = 349 rad/s. What is the maximum value E max of the induced electric field at a perpendicular distance 1.85 cm from the axis of the solenoid?

Explanation:

Flux

Φ = B A

= πR²B

-dΦ / dt = -πR²dB/ dt

EMF = - πR².00275d.cos ( ω t )/ dt

EMF = ( πR².00275/ω) sin ω t

EMFmax = ( πR².00275/ω)

EMFmax = ∫ E dR , E is elecreic field at distance R from the axis

= 2πR X E

( πR².00275/ω) = 2πR X Emax

Emax = R x .00275/2ω

= 1.85 x 10⁻² x .00275 / (2 x 349)

= .7288 x 10⁻⁷ N/C  

= 7.288 x 10⁻⁸ N/C

real, smaller and upside-down.   so the answer should be b.