A car generator turns at 400 rpm (revolutions per minute) when the engine is idling. It has a rectangular coil with 300 turns of dimensions 5.00 cm by 6.46 cm that rotates in an adjustable magnetic field. What is the field strength needed to produce a 24.0 V peak emf

The field strength needed to produce a 24.0 V peak emf is 0.5913 T

Explanation:

From the formula for maximum emf of a generator,

∴

Where N is the number of loops

A is cross section of loops

B is magnetic field strength

ω is the angular frequency of loops

From the question,

N = 300 turns

A = l × b ( since it is a rectangular coil)

A = 6.46 cm × 5.00 cm

A = 0.0646 m × 0.05 m

A = 0.00323 m²

ω = 400 rpm = (400/60)×2π rad/s

ω = 41.8879 rad/s

Putting all the parameters into the formula

Hence, the field strength needed to produce a 24.0 V peak emf is 0.5913 T

i think the answer is a, hope this is right, that would be my best guess.