Consider a square with sides of length 5.0 cm, as shown in the diagram. An elect
ID: 1549096 • Letter: C
Question
Consider a square with sides of length 5.0 cm, as shown in the diagram. An electron is fixed at point P in the upper corner of the square. There is also a very long wire that runs along the bottom edge of the square carrying a current with a magnitude of 17 mA in the direction indicated by the diagram.
A. What is the electric field at point Q? [Give both magnitude and direction.]
B. What is the magnetic field at point Q? [Give both magnitude and direction.]
C. Suppose a particle with charge 4.9 uC passes through point Q with a velocity of 5.2 m/s pointed at an angle of 30 degrees above the +x-axis. What is the net force acting on this particle? [Give both magnitude and direction.]
P I Q XExplanation / Answer
(A) E = k q / a^2
= (9 x 10^9 x 1.602 x 10^-19) / (0.05^2)
= 5.767 x 10^-7 N/C
along +ve x axis.
(B) B = u0 I / 2 pi a
= (4 x pi x 10^-7) (17 x 10^-3) / (2 x pi x 0.05)
= 6.8 x 10^-8 T
into the page OR along -ve z axis.
(C) v = 5.2 m/s ( cos30 i + sin30 j) = 4.50i + 2.6j m/s
electric force , Fe = q E
= (4.9 x 10^-6) ( 5.767 x 10^-7 i)
= 2.825 x 10^-12 N
Magnetic force, Fm = q (v X B)
= (4.9 x 10^-6) [ (4.50i + 2.6j) x (-6.8 x 10^-8 k) ]
= 1.50 x 10^-12 j - 0.867 x 10^-13 i
F = Fm + Fe
Magnitude = sqrt(2.825^2 + 1.50^2 + 0.867^2) = 3.314 x 10^-12 N