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## Electrostatics

(This section must be read in conjunction with the CAPS, p. 84–85.)

### Coulomb's law

• State Coulomb's law:
The magnitude of the electrostatic force exerted by one point charge (Q1 ) on another point charge (Q2 ) is directly proportional to the product of the magnitudes of the charges and inversely proportional to the square of the distance (r) between them:
• Solve problems using the equation:

for charges in one dimension (1D)
(restrict to three charges).
• Solve problems using the equation:

for charges in two dimensions (2D)
– for three charges in a right-angled formation
(limit to charges at the 'vertices of a right- angled triangle').

### Electric field

• Describe an electric field as a region of space in which an electric charge experiences a force. The direction of the electric field at a point is the direction that a positive test charge would move if placed at that point.
• Draw electric field patterns for the following configurations:
• A single point charge
• Two point charges (one negative, one positive OR both positive OR both negative)
• A charged sphere
• NOTE:
Restrict to situations in which the charges are identical in magnitude.
• Define the electric field at a point:
The electric field at a point is the electrostatic force experienced per unit positive charge placed at that point.
In symbols:
• Solve problems using the equation:
• Calculate the electric field at a point due to a number of point charges, using the equation:

to determine the contribution to the field due to each charge.
Restrict to three charges in a straight line.