SPH 4U1
Coulomb’s Law and Electric Fields
1.
A +70 μC charge and a -80 μC charge are 70 cm apart. If a +48μC charge is placed halfway between
them, what net force will each charge experience due to the other two charges?(140N[left],
530N[right], 390 N[left])
2.
A +2.7 μC charge and a -3.5 μC charge are placed 25 cm apart. Where can a third charge be placed
so it experiences no net force? (1.8 m beyond the positive charge)
3.
What is the magnitude and direction of the acceleration experienced by an electron in an electric
field of 500 N/C? (8.8x1013m/s2, in the direction opposite the field)
4.
A proton is released in a uniform electric field and experiences a force of 3.2x10-14N toward the
south. What is the magnitude and direction of the electric field? (2.0 x 105 N/C [south])
5.
An electron is released from rest in a uniform electric field and accelerates to the north at 125 m/s2.
What are the magnitude and direction of the electric field? (7.12x10-10N/C [south])
6.
Calculate the electric field at the centre of a square 60.0 cm on a side if one corner is occupied by a
+45 μC charge, and the other three are occupied by -31.0 μC charges. (3.8 x 106N/C, along the
diagonal away from the positive charge)
7.
(A toughie!) Two nonconducting spheres have a total charge of 90.0 μC. When placed 1.20 m apart,
the force each exerts on the other is 12.0 N and is repulsive. What is the charge on each? (55.3 μC,
34.7 μC) What if the force were attractive? (-17.8 μC, 108 μC)