PHYS
S13Phys2BaLec26A

# The electron at the switch isnt the one that will

• Notes
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The electron at the switch isn’t the one that will give energy to the lights. When you turn on a light switch you are establishing an electric field that moves all the free electrons in the wire circuit. You need a closed loop with the wire. An open loop means no electric field and no current flow. This is known as an open circuit.

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Current Looking at charges moving from the discharge of a capacitor, the conventional current I is in the direction of the electric field. The electron current (the motion of the actual charge carriers) will be opposite the direction of the electric field. But due to historical reasons, we use positive current when performing calculations.
Current When a battery is placed in a closed loop an electric field is established inside the conducting wire. This electric field starts on the positive terminal and ends on the negative terminal. Positive charges will move with the electric field toward the negative terminal. When the circuit is open, the positive charges don’t see a negative terminal and thus, no current.

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Current The potential difference created by the battery terminal is also called EMF (ElectroMotive Force). This is a silly name as EMF is measured in Volts. We physically measure the amount of current in a circuit with an ammeter. You connect the ammeter in the circuit in series with the element you are trying to measure the current of.
“Break open” to detect flow Ammeter + A

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Current A voltmeter is used to measure electric potential difference (or voltage). You connect a voltmeter in the circuit in parallel to the element you are trying to measure the potential difference of.
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• Spring '08
• schuller
• Physics, Potential difference, Electric charge, Integrity of Scholarship

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