In: Physics
Three point charges have equal magnitudes, two being positive and one negative. These charges are fixed to the corners of an equilateral triangle, as the drawing shows. The magnitude of each of the charges is 3.5 μC, and the lengths of the sides of the triangle are 2.0 cm. Calculate the magnitude of the net force that each charge experiences.
The force experienced by the positive charge (say at the top
corner of the equilateral triangle )due to another positive charge
is
F = k q2 / r2
Where q is the charge and r is the distance between the
charges
F = 9 x 109 x (3.5 x 10-6)2 /
(0.02 m)2
F = 275.62 N
This is directed away from the positive charge along the line
joining the two charges
The force on the positive charge due to the negative charge
is
F = k q2 / r2
F = 9 x 109 x (3.5 x
10-6)2 / (0.02 m)2
F = 275.62 N
This force directed towards the negative charge
To find the net force on the positive charge
When we make the forces in their component form, we can see that
the vertical components (F sin ) cancels and the
parallel components gets added
The net force is
Fnet = 2 F cos
Where is the angle
between the force and the horizontal direction.
Fnet = 2 x 275.62 x cos 600
Fnet = 275.62 N
Directed horizontally towards the right or left (depending on where
the negative charge resides)
The force experienced by the other positve charge due to
positive and negative charges is the same as the above
case.
For the negative charge, the force is due to both positive
charges
The force experienced is
F = F = k q2 / r2
F = 9 x 109 x (3.5 x
10-6)2 / (0.02 m)2
F = 275.62 N
Both the forces are directed towards the positve charge.
The two forces are separated by an angle of 600. Thus
the net force is
Fnet = sqrt (F2 + F2 + 2
F2 cos 600)
Fnet = sqrt(3) F
Fnet = 1.732 x 275.62 N = 477.39 N
Fnet = 477.39 N