Question

Difficulty: EasyElectrostatics and Electric Charges

What is the magnitude of the electric field intensity, in N C1\text{N C}^{-1}, at a point 2.0 m2.0\text{ m} away from a isolated point charge of +4.0×106 C+4.0 \times 10^{-6}\text{ C} in a vacuum? (Take Coulomb's constant k=9.0×109 N m2 C2k = 9.0 \times 10^9\text{ N m}^2\text{ C}^{-2})

Answer: 9000 N C^-1

Answer

The magnitude of the electric field intensity is 9000 N C19000\text{ N C}^{-1}.
The electric field intensity EE produced by a point charge qq at distance rr is given by E=kqr2E = \frac{kq}{r^2}. Substituting k=9.0×109 N m2 C2k = 9.0 \times 10^9\text{ N m}^2\text{ C}^{-2}, q=4.0×106 Cq = 4.0 \times 10^{-6}\text{ C}, and r=2.0 mr = 2.0\text{ m} yields E=9.0×109×4.0×1064.0=9000 N C1E = \frac{9.0 \times 10^9 \times 4.0 \times 10^{-6}}{4.0} = 9000\text{ N C}^{-1}.

Step-by-Step Solution

1
Identify the given physical quantities and formula
q=4.0×106 Cq = 4.0 \times 10^{-6}\text{ C}, r=2.0 mr = 2.0\text{ m}, k=9.0×109 N m2 C2k = 9.0 \times 10^9\text{ N m}^2\text{ C}^{-2}. Formula: E=kqr2E = \frac{kq}{r^2}
The magnitude of electric field intensity due to a single point charge is given by Coulomb's field law.
2
Substitute the values and calculate the electric field strength
E=9.0×109×4.0×1062.02=360004=9000 N C1E = \frac{9.0 \times 10^9 \times 4.0 \times 10^{-6}}{2.0^2} = \frac{36000}{4} = 9000\text{ N C}^{-1}
Perform basic arithmetic simplification to determine the numerical result.

Key Concept

Electric Field Intensity due to a Point Charge
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