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Magnifying Glass Tilted Right

Theme D - Fields

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Rocket

Theme A - Space, Time & Motion

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Thermometer

Theme B - The Particulate Nature Of Matter

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Water Wave

Theme C - Wave Behaviour 

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Microscope

Theme E - Nuclear & Quantum Physics

<ul>
	<li>An isolated charge in space creates an electric field.</li>
	<li>Electric field strength is the force per unit positive charge at a point in the field.</li>
	<li>It is represented by the letter E and measured in Newtons per Coulomb (N/C).</li>
</ul>

<ul>
	<li>Imagine a charge (q) and a point P, a distance (r) away from the charge.</li>
	<li>We use a positive test charge (qt) at P, and measure the force (F) that acts on the test charge due to the isolated charge.</li>
	<li>The formula for the electric force on the test charge is: F = (k &times; q &times; qt) / r&sup2;</li>
	<li>Electric field strength (E) is calculated as: E = F/qt</li>
	<li>This simplifies to: E = (k &times; q &times; qt / r&sup2;) / qt = (k &times; q) / r&sup2;</li>
	<li>E can also be calculated as: E = q / (4&pi;&epsilon;0 &times; r&sup2;), where &epsilon;0 is the permittivity of free space.</li>
</ul>

<ul>
	<li>Test charges and small current elements affect the fields they are used to measure.</li>
	<li>These test objects are imaginary constructs to help understand fields.</li>
	<li>A gedankenexperiment is a thought experiment used to understand concepts that cannot be practically measured or observed.</li>
</ul>

<ul>
	<li>Example 4 - Oxygen nucleus with charge of +8e at a distance of 0.68nm. a. Elementary charge (e) = 1.6 &times; 10⁻&sup1;⁹C. b. Oxygen nucleus charge = 8 &times; 1.6 &times; 10⁻&sup1;⁹C. c. Distance (r) = 6.8 &times; 10⁻&sup1;⁰m. d. E = (1.3 &times; 10⁻&sup1;⁸) / (4&pi;&epsilon;0 &times; (6.8 &times; 10⁻&sup1;⁰)&sup2;) = +2.5 &times; 10&sup1;⁰NC⁻&sup1; (away from the nucleus).</li>
	<li>Example 5 - Calculate the electric field strengths in a vacuum. a. At 1.5cm from a +10&mu;C charge. i. Convert: r = 1.5 &times; 10⁻&sup2;m, q = 1.0 &times; 10⁻⁵C. ii. E = (1.0 &times; 10⁻⁵) / (4&pi;&epsilon;0 &times; (1.5 &times; 10⁻&sup2;)&sup2;) = +4.0 &times; 10⁸NC⁻&sup1; (away from the positive charge). b. At 2.5m from a &ndash;0.85mC charge. i. Convert: r = 2.5m, q = &ndash;8.5 &times; 10⁻⁴C. ii. E = (&ndash;8.5 &times; 10⁻⁴) / (4&pi;&epsilon;0 &times; 2.5&sup2;) = &ndash;1.2 &times; 10⁶NC⁻&sup1; (towards the negative charge).</li>
</ul>

<ul>
	<li>Metal detectors - The detector sends out an electric field, and when it encounters a metal object, it disrupts the field, triggering the detector.</li>
	<li>Lightning - A strong electric field forms between the ground and the cloud, which leads to the flow of electrical energy and a lightning bolt.</li>
</ul>

The word &quot;gedankenexperiment&quot; is German for &quot;thought experiment.&quot; It&#39;s a concept used in science to explore hypothetical scenarios and understand how certain principles might apply in those cases.

Theme D - Fields

Electric Field Strength From Point Charges Explained

Table of content

Basics of electric field strength

Calculating electric field strength

The gedankenexperiment

Unlock the Full Content!

Theme D - Fields

Electric Field Strength From Point Charges Explained

Table of content

Basics of electric field strength

Calculating electric field strength

The gedankenexperiment

Unlock the Full Content!