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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

Concept

<ul>
	<li>An electronvolt (eV) is a unit of energy used in physics.</li>
	<li>It&#39;s the amount of energy an electron gains (or loses) when it moves through a potential difference of one volt.</li>
	<li>It&#39;s a small unit, which makes it convenient for dealing with tiny amounts of energy.</li>
</ul>

Real-world Example

<ul>
	<li>Imagine a roller coaster. When it&#39;s at the top of a hill, it has potential energy. As it goes down the hill, it converts this potential energy into kinetic energy (energy of motion). In a similar way, electrons gain energy when they move through a voltage difference.</li>
</ul>

Conversion

<ul>
	<li>1 eV is equal to 1.6 &times; 10-19&nbsp;&nbsp;J (joules).</li>
</ul>

Concept

<ul>
	<li>When an electron is accelerated through a potential difference, it gains kinetic energy.</li>
</ul>

Example

<ul>
	<li>Imagine a skateboarder (electron) going down a steep ramp (potential difference). The steeper the ramp, the faster the skateboarder goes. The skateboarder&#39;s speed represents the kinetic energy.</li>
</ul>

Calculation

<ul>
	<li>An electron accelerated through 180V gains 180eV of energy.</li>
	<li>Using the conversion factor, 180eV = 2.9 &times; 10^(-17) J.</li>
</ul>

Calculation

<ul>
	<li>Kinetic energy = 0.5 &times; mass &times; speed2.</li>
	<li>Solving for speed: speed = &radic;(2 &times; kinetic energy / mass).</li>
	<li>Plugging in numbers: speed = &radic;(2 &times; 2.9 &times; 10-17&nbsp;/ 9.1 &times; 10-31) = 8.0 &times; 106 m/s.</li>
</ul>

Concept

<ul>
	<li>Protons, like electrons, can also be accelerated and gain energy.</li>
</ul>

Example

<ul>
	<li>Imagine a baseball (proton) being thrown (accelerated) by a pitcher. The baseball gains energy and moves faster.</li>
</ul>

Calculation

<ul>
	<li>Energy gained by proton = 4.0 &times; 10-11&nbsp;J.</li>
	<li>Solving for speed: speed = &radic;(2 &times; energy / mass).</li>
	<li>Using mass of proton: speed = &radic;(2 &times; 4.0 &times; 10-11&nbsp;/ 1.7 &times; 10-27) = 2.2 &times; 108 m/s (70% speed of light).</li>
</ul>

Note

<ul>
	<li>Actual speed will be less due to relativistic effects. As protons gain energy, they also gain mass, which affects their speed.</li>
</ul>

Concept

<ul>
	<li>This experiment measures how electric field strength varies with voltage, plate area, and plate distance.</li>
</ul>

Real-world Example

<ul>
	<li>Imagine a sandwich (parallel plates). The filling represents the electric field. If you press the sandwich, the filling spreads out (change in distance). If you add more filling, the sandwich becomes thicker (change in plate area).</li>
</ul>

Procedure

<ul>
	<li>Set up parallel plates, power supply, insulated lead, and coulombmeter.</li>
	<li>Set voltage V on power supply, measure distance d between plates.</li>
	<li>Turn on power, touch flying lead to plate, charge plates.</li>
	<li>Zero coulombmeter, touch probe to charged plate, record charge q.</li>
	<li>Change distance d, repeat measurements.</li>
	<li>Use plates with different areas A, repeat measurements.</li>
	<li>Change voltage V, repeat measurements.</li>
	<li>Plot results: q vs. V, q vs. A, q vs. d.</li>
</ul>

Safety Note

<ul>
	<li>This experiment uses high voltages. Be careful not to touch the plates or the power supply terminals when they are charged. Always switch off the power supply before adjusting the plates.</li>
</ul>

Remember to always ask your teacher if you have any questions about these concepts! Happy studying!

Electronvolt: The Powerhouse of Particle Physics

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Standard Level

Physics SL

Theme D - Fields

Electronvolt: The Powerhouse of Particle Physics

Table of content

What is an electronvolt (eV)?

Worked example 9 - electron gains kinetic energy

Unlock the Full Content!

Theme D - Fields

Electronvolt: The Powerhouse of Particle Physics

Table of content

What is an electronvolt (eV)?

Worked example 9 - electron gains kinetic energy

Unlock the Full Content!