An electric motor contains a 250-turn circular coil 6.2cm in diameter. . . If it is to develop a maximum torque of 2.0N*m at a current of 3.9A , what should be the magnetic field strength?

The magnetic field strength is 0.679 T.

Explanation:

Given:

Number of turns (N) = 250

Current in the coil (I) = 3.9 A

Diameter of the coil (d) = 6.2 cm =0.062 m [1 cm = 0.01 m]

Maximum torque is,

First, let us calculate the area of the coil.

Area is given by the formula:

Now, the torque acting on the circular coil is given by the formula:

Now, torque is maximum when the angle ° or

Therefore, the maximum torque is given as:

Now, plug in the given values and solve for 'B'. This gives,

Therefore, the magnetic field strength is 0.679 T.

answer: the exterior temperature of commercial jet planes as they leave the stratosphere and return to the ground increases steadily.

explanation:

the lower most layer of atmosphere is troposphere which extends from 0 to 12 km above the surface of the earth. the temperature initially decreases as distance is increased from the earth's surface. commercial jets fly in lower part of the stratosphere. the stratosphere extends upto 50 km. the temperature in stratosphere starts rising again due to presence of ozone which traps the uv rays.

thus, when the planes leave the stratosphere and return to the ground, the exterior temperature increases steadily.