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What's the electric field strength in a region where the flux through a \(1.0 \mathrm{cm} \times 1.0 \mathrm{cm}\) flat surface is \(65 \mathrm{N} \cdot \mathrm{m}^{2} / \mathrm{C},\) if the field is uniform and the surface is at right angles to the field?

Short Answer

Expert verified
The strength of the electric field is \(650000 \mathrm{N/C}\).

Step by step solution

01

Understanding the given problem

The problem gives us the flux (\(\Phi = 65 \mathrm{N} \cdot \mathrm{m}^{2} / \mathrm{C}\)) through a flat surface of area \(1.0 \mathrm{cm} \times 1.0 \mathrm{cm}\), or \(0.01 \mathrm{m} \times 0.01 \mathrm{m}\). The electric field is uniform across the surface and the surface is at right angles to the field, so we can directly apply the relation \(\Phi =EA\). We can rearrange this equation to solve for the electric field.
02

Convert area from cm to m

Before we start calculations, convert the given area from \(\mathrm{cm}^2\) to \(\mathrm{m}^2\) to match the unit of the electric flux. \(1 \mathrm{m} = 100 \mathrm{cm}\), so \( (1.0 \mathrm{cm})^2 = (0.01 \mathrm{m})^2 = 0.0001 \mathrm{m}^2 \).
03

Calculate the electric field strength

Rearranging the equation from step 1, we get \(E=\Phi /A\), i.e., the electric field strength equals the electric flux divided by the area. Substituting the given values, \(E = 65 \mathrm{N} \cdot \mathrm{m}^{2} / \mathrm{C} / 0.0001 \mathrm{m}^2\) , we find that the electric field strength is \(650000 \mathrm{N/C}\).

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Electric Flux
Electric flux is a fundamental concept in electromagnetism. It measures the amount of electric field passing through a certain area. You can visualize it as counting the number of electric field lines passing through a surface.
In this exercise, the electric flux is given as \(65 \, \mathrm{N} \cdot \mathrm{m}^2 / \mathrm{C}\). The formula used to calculate electric flux, when the surface is perpendicular to the electric field, is:
  • \( \Phi = E \cdot A \)
Where \(\Phi\) is the electric flux, \(E\) is the electric field strength, and \(A\) is the area of the surface.
The relation becomes straightforward when the field is uniform, meaning the strength and direction of the field are the same across the surface. In this problem, this relationship helps us determine the electric field with the flux and area known.
Uniform Electric Field
A uniform electric field is one where the electric field strength is the same at every point. It doesn't change direction or magnitude. This scenario greatly simplifies calculations.
In this exercise, the electric field is uniform over the 1.0 cm x 1.0 cm surface. When a field is uniform, it implies that:
  • The angle between the electric field and the surface affects calculations, but here it’s perpendicular, with an angle of zero degrees.
  • The electric field lines are parallel and equidistant, spreading equally over the surface area.
  • This assumption allows us to use the formula \(\Phi = E \cdot A\) directly, with minimal additional considerations.
This consistency simplifies determining the electric field strength as we don't need to account for any variations across the surface.
Area Conversion
When dealing with physics problems, paying careful attention to units is crucial. In this exercise, we initially have the area in square centimeters (\(\mathrm{cm}^2\)) which needs conversion to square meters (\(\mathrm{m}^2\)). Consistent units are indispensable for calculations.
To convert from \(\mathrm{cm}^2\) to \(\mathrm{m}^2\):
  • Understand that 1 meter equals 100 centimeters. Thus, 1 square centimeter means \((0.01 \text{ m})^2 = 0.0001 \text{ m}^2\).
  • For the given area, \(1.0 \mathrm{cm} \times 1.0 \mathrm{cm}\) translates to \(0.0001 \mathrm{m}^2\).
This conversion ensures that the electric flux value (in \(\mathrm{N} \cdot \mathrm{m}^2 / \mathrm{C}\)) aligns with the area, ensuring calculations for the electric field strength (\(\mathrm{N/C}\)) are accurate. Always verify units at the start to prevent errors later in the problem.

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Most popular questions from this chapter

A study shows that mammalian red blood cells (RBCs) carry electric charge resulting from 4.4 million (rabbit cells) to 15 million (human cells) excess electrons spread over their surfaces. Approximating rabbit and human RBCs as spheres with radii \(30 \mu \mathrm{m}\) and \(36 \mu \mathrm{m},\) respectively, find the electric field strengths at the cells' surfaces.

The electric field of a flat sheet of charge is \(\sigma / 2 \epsilon_{0} .\) Yet the field of a flat conducting sheet-even a thin one, like a piece of aluminum foil- is \(\sigma / \epsilon_{0} .\) Explain this apparent discrepancy.

An infinitely long rod of radius \(R\) carries a uniform volume charge density \(\rho .\) Show that the electric field strengths outside and inside the rod are given, respectively, by \(E=\rho R^{2} / 2 \epsilon_{0} r\) and \(E=\rho r / 2 \epsilon_{0},\) where \(r\) is the distance from the rod axis. (Although an infinite rod is an impossibility, your answer is a good approximation for the field of a finite rod whose length is much greater than its diameter.)

The charge density within a uniformly charged sphere of radius \(R\) is \(\rho=\rho_{0}-a r^{2},\) where \(\rho_{0}\) and \(a\) are constants and \(r\) is the distance from the center. Find an expression for \(a\) such that the electric field outside the sphere is zero.

Eight field lines emerge from a closed surface surrounding an isolated point charge. Would the number of field lines change if a second identical charge were brought to a point just outside the surface? If not, would anything change? Explain.

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