Answer:

Explanation:
Given,
Magnetic field,B = 0.5 x 10⁻⁴ T
distance,r= 15 cm = 0.15 m
Current = ?
Using Ampere's law of magnetic field




Current in the wire is equal to 
That's what happens if there is more than one force acting on the
object, and the forces are balanced, that is, they all "cancel out".
Think of the rope in a Tug-'o-War. It has 50 musclebound football guys
all pulling the rope to the west, and 150 strong cheerleaders all pulling
the rope to the east. The total force to the west is exactly equal to the
total force to the east, and the rope doesn't move at all. The forces on it
are balanced, and the effect on its motion is the same as if there were
no force on it at all.
Answer:
The unit that is a radical among the options is;
a. NH₄⁺
Explanation:
A radical is an atom, group of atoms molecule or ion that contains an electron that is unpaired. The presence of the unpaired electrons make radical very reactive as such most radicals enter into reactions with other species or with themselves to form new compounds making them not last long.
Radicals are also known as free radicals. Examples of radicals includes; Ammonium ion, NH₄⁺
Nitrate ion NO₃⁻ (From a salt)
Hydroxide ion OH⁻ (From a base)
Sulphate ion SO₄²⁺ (From an acid)
All of which are formed in aqueous solution of acids, salts and bases.