What couple is needed to hold a small single-turn coil of area 5 cm2 in equilibrium, when it carries a current of 10 a and is placed with its axis at right angles to a field of flux density 0.15 t. what couple would be required if the coil had 20 turns?

time taken, t = 20 seconds

Explanation:

It is given that, a projectile is thrown upward so that its distance above the ground after t seconds is given by the function as :

.....(1)

t be the time taken to reach its maximum height.

For maximum height,  

After solving, we get t = 20 seconds

Putting the value of t is equation (1) as :

h(t) = 6400 meters

Hence, the time taken to reach its maximum height is 20 seconds.