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<h2 class="title">Current: Flow of Charge</h2>
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<p>When we talk about current we talk about how much charge moves past a fixed point in circuit in one second. Think of charges being pushed around the circuit by the battery, there are charges in the wires but unless there is a battery they won't move.</p>
<p>When one charge moves the charges next to it also move. They keep their spacing as if you had a tube of marbles like in this picture or looked at a train and its carriages.</p>
<img alt="4d09b327d9edbf52bc406a7ee62a216a.png" src="https://data.ulearngo.com/assets/8ab1963d-b586-4c9b-aeda-c2d9ad4dbf98"/>
<p>If you push one marble into the tube one must come out the other side, if a train locomotive moves all the carriages move immediately because they are connected. This is similar to charges in the wires of a circuit.</p>
<p>The idea is that if a battery started to drive charge in a circuit all the charges start moving instantaneously.</p>
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<h3>Did You Know?</h3>
<p>Benjamin Franklin made a guess about the direction of charge flow when rubbing smooth wax with rough wool. He thought that the charges flowed from the wax to the wool (i.e. from positive to negative) which was opposite to the real direction. Due to this, electrons are said to have a <em>negative</em> charge and so objects which Ben Franklin called “negative” (meaning a shortage of charge) really have an excess of electrons. By the time the true direction of electron flow was discovered, the convention of “positive” and “negative” had already been so well accepted in the scientific world that no effort was made to change it.</p>
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<p><strong>Copper wire</strong></p>
<div class="wp-caption alignnone" style="width: 318px"><img alt="" height="320" src="https://data.ulearngo.com/assets/f0ccd0f7-05be-4395-9988-a8c2c346c1d5" width="318"/><p class="wp-caption-text">Photography on Flickr.com</p></div>
<div class="ns-school-emp">
<h3>Definition: Current</h3>
<div class="ns-school-defn">
<p>Current is the rate at which charges moves past a fixed point in a circuit. The units of current are the ampere (A) which is defined as one coulomb per second.</p>
<p>Quantity: Current (I)         Unit name: ampere        Unit symbol: A</p>
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<p><strong>Plasma ball</strong></p>
<div class="wp-caption alignnone" style="width: 316px"><img alt="" height="320" src="https://data.ulearngo.com/assets/51a43403-3293-430f-8a22-bb772df2782d" width="316"/><p class="wp-caption-text">Photography by ahisgett on Flickr.com</p></div>
<p>We use the symbol I to show current and it is measured in amperes (A). One ampere is one coulomb of charge moving in one second ($\text{C·s$^{-1}$}$).</p>

\[I = \frac{Q}{\Delta t}\]

<p>When current flows in a circuit we show this on a diagram by adding arrows. The arrows show the direction of flow in a circuit. By convention we say that charge flows from the positive terminal on a battery to the negative terminal.</p>
<p>If the voltage is high enough a current can be driven through almost anything. In the plasma ball example on the left, a voltage is created that is high enough to get charge to flow through the gas in the ball. The voltage is very high but the resulting current is very low. This makes it safe to touch.</p>
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Flow of Charge

Physics is a science discipline concerned with the nature and properties of matter and energy. Physics topics include mechanics, heat, light and radiation, sound, electricity, magnetism, the structure of atoms, and so on.

Physics

Explore the principles of electric circuits, including potential difference, flow of charge, resistance, Ohm&#8217;s Law, resistor networks, and batteries, with a focus on understanding how to evaluate internal resistance in circuits and the use of power and energy in electrical systems.


Flow of Charge

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