NUMERICAL PROBLEMS
TOPIC: COULOMBS LAW
, 1) Two point charges, +4 µC and -6 µC, are separated by a distance of 0.3 m. Calculate the
electrostatic force between them.
1. Identify the given values:
q1 = +4 µC = +4 x 10^-6 C
q2 = -6 µC = -6 x 10^-6 C
r = 0.3 m
Coulomb's constant (k) = 8.99 x 10^9 Nm²/C²
2. Apply Coulomb's Law:
Coulomb's Law states: F = k * |q1 * q2| / r²
Where:
F is the electrostatic force
k is Coulomb's constant
q1 and q2 are the magnitudes of the charges
r is the distance between the charges
3. Substitute the values:
F = (8.99 x 10^9 Nm²/C²) * |(4 x 10^-6 C) * (-6 x 10^-6 C)| / (0.3 m)²
4. Calculate the force:
F ≈ 0.24 N
5. Determine the direction:
Since the charges have opposite signs (one positive and one negative), the force is attractive.
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2) What is the force between two identical charges of +2 µC separated by 0.5 m?
1. Identify the given values:
q1 = +2 µC = +2 x 10^-6 C
q2 = +2 µC = +2 x 10^-6 C
r = 0.5 m
Coulomb's constant (k) = 8.99 x 10^9 Nm²/C²
, 2. Apply Coulomb's Law:
F = k * |q1 * q2| / r²
3. Substitute the values:
F = (8.99 x 10^9 Nm²/C²) * |(2 x 10^-6 C) * (2 x 10^-6 C)| / (0.5 m)²
4. Calculate the force:
F ≈ 0.144 N
5. Determine the direction:
Since both charges are positive, the force is repulsive (they push away from each other).
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3) Two charges exert a force of 12 N on each other. If the distance between them is doubled, what
will be the new force?
1. Understand the relationship:
Coulomb's Law (F = k * |q1 * q2| / r²) shows that the force (F) is inversely proportional to the square of
the distance (r²). This means:
If you double the distance (r becomes 2r), the force becomes 1/(2²)=1/4 of the original force.
2. Apply the relationship:
Since the distance is doubled, the new force (F') will be:
F' = F / 2²
F' = F / 4
3. Substitute the given value:
The original force (F) is 12 N. Therefore:
F' = 12 N / 4
F' = 3 N
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4) Two charges of +5 nC and -10 nC are 2 cm apart. Find the force between them.
1.Identify the given values:
q1 = +5 nC = +5 x 10⁻⁹ C
TOPIC: COULOMBS LAW
, 1) Two point charges, +4 µC and -6 µC, are separated by a distance of 0.3 m. Calculate the
electrostatic force between them.
1. Identify the given values:
q1 = +4 µC = +4 x 10^-6 C
q2 = -6 µC = -6 x 10^-6 C
r = 0.3 m
Coulomb's constant (k) = 8.99 x 10^9 Nm²/C²
2. Apply Coulomb's Law:
Coulomb's Law states: F = k * |q1 * q2| / r²
Where:
F is the electrostatic force
k is Coulomb's constant
q1 and q2 are the magnitudes of the charges
r is the distance between the charges
3. Substitute the values:
F = (8.99 x 10^9 Nm²/C²) * |(4 x 10^-6 C) * (-6 x 10^-6 C)| / (0.3 m)²
4. Calculate the force:
F ≈ 0.24 N
5. Determine the direction:
Since the charges have opposite signs (one positive and one negative), the force is attractive.
___________________________________________________________________________
2) What is the force between two identical charges of +2 µC separated by 0.5 m?
1. Identify the given values:
q1 = +2 µC = +2 x 10^-6 C
q2 = +2 µC = +2 x 10^-6 C
r = 0.5 m
Coulomb's constant (k) = 8.99 x 10^9 Nm²/C²
, 2. Apply Coulomb's Law:
F = k * |q1 * q2| / r²
3. Substitute the values:
F = (8.99 x 10^9 Nm²/C²) * |(2 x 10^-6 C) * (2 x 10^-6 C)| / (0.5 m)²
4. Calculate the force:
F ≈ 0.144 N
5. Determine the direction:
Since both charges are positive, the force is repulsive (they push away from each other).
___________________________________________________________________________
3) Two charges exert a force of 12 N on each other. If the distance between them is doubled, what
will be the new force?
1. Understand the relationship:
Coulomb's Law (F = k * |q1 * q2| / r²) shows that the force (F) is inversely proportional to the square of
the distance (r²). This means:
If you double the distance (r becomes 2r), the force becomes 1/(2²)=1/4 of the original force.
2. Apply the relationship:
Since the distance is doubled, the new force (F') will be:
F' = F / 2²
F' = F / 4
3. Substitute the given value:
The original force (F) is 12 N. Therefore:
F' = 12 N / 4
F' = 3 N
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4) Two charges of +5 nC and -10 nC are 2 cm apart. Find the force between them.
1.Identify the given values:
q1 = +5 nC = +5 x 10⁻⁹ C
