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hello tis the first slide aka basic explain
Transcript of hello tis the first slide aka basic explain
Uses of Capacitors
Some of the many uses are...
Light Sensitive Switch
So firstly, what is a light sensitive switch?
Light Sensitive Switches Uses
Light Sensitive Switches & Capacitors
Light sensitive switches are ones which work by responding to changes in light levels; a 'photocell' is a type of resistor that decreases in resistance when it is exposed to light. Also known as photoresistor, light-dependent resistor, and photoconductor.
For example when it is daytime, the light sensitive switch will detect an increase in light levels and automatically switch off.
A capacitor is a device used to store electric charge.
So how do they work?
2 plates (conductors)
Separated by any insulator
The plates acquire a charge when a voltage (p.d) is applied
The plate connected to the positive terminal of the battery acquires a positive charge
The plate connected to the negative terminal of the battery acquires a negative charge
The charge the capacitor gains has the same volage as the battery it is connected to
Charges remain after battery is disconnected
By doubling the voltage you can double the amount of charge on the plate. Hence, the so called “capacitance” of a capacitor is measured by how much charge per volt the device can carry.
Capacitors in a circuit...
Here you have a capacitor, battery and bulb. If you remove the battery and replace it with a wire after it the capacitor is fully charged:
The charges will flow from one plate to another
The bulb will remain lit
The bulb will begin to dim till the capacitor is discharged
Special capacitors are made to supply huge current pulses to “pulsed powered” devices and application. Examples of these pulse power applications are pulse power lasers and particle accelerators.
Since capacitors can store charge, they are used in many electrical devices to allow them to keep working while the batteries are being replaced. This is to prevent loss of important device memory. Ex: Large capacitors are used in car radio systems to provide extra power to the amplifiers when needed
But how do Light Sensitive Switches work?
Design and Technology. (n.d.). GCSE Bitesize. Retrieved January 14, 2014, from http://www.bbc.co.uk/schools/gcsebitesize/design/electronics/componentsrev5.shtsml
How Capacitors Work. (n.d.).HowStuffWorks. Retrieved January 13, 2014, from http://electronics.howstuffworks.com/capacitor.htm
Revision Notes - Physics - igcse - Electric Circuits. (n.d.). Online Resource of Physics. Retrieved January 14, 2014, from http://www.physicsatweb.com/rev.php?id=Electric%20Circuits&rid=18
Richard, A. (2011, March 16). Uses of Capacitors | eHow. eHow. Retrieved January 14, 2014, from http://www.ehow.com/info_8069050_uses-capacitors.html
AP Technologies. (n.d.). Photodiode Theory of Operation. Retrieved January 7, 2014, from http://www.aptechnologies.co.uk/support/photodiodes/photodiode-theory-of-operation
Electron volt - Definition. (n.d.). Retrieved January 7, 2014, from http://www.merriam-webster.com/dictionary/electron%20volt
Marian, P. (n.d.). Light Sensitive Switch Circuit. Retrieved January 7, 2014, from http://www.electroschematics.com/4865/light-sensitive-switch-circuit/
Photodiode/Phototransistor Application Circuit. (n.d.). Retrieved January 7, 2014, from http://physlab.lums.edu.pk/images/1/10/Photodiode_circuit.pdf
Rouse, M. (2008, May). What is hole? Retrieved January 7, 2014, from http://whatis.techtarget.com/definition/hole
First, some definitions:
A photon is a fundamental particle of light that is both massless and has no electrical charge.
An electron hole is the opposite of an electron; it is the term used for the lack of an electron where one could be present.
An eV is the unit of measurement used to describe the energy gained or lost by an electron when passed through an (electrical) potential difference of one volt.
When a photon of energy greater than 1.1 eV strikes the diode in the device, it creates pairs of electron holes. The lower the energy of a photon, the deeper it is absorbed. If this absorption happens in the depletion region, the carriers are taken from the junction by the electric field present in the depletion region. Then, the electron holes move towards the anode and the electrons more towards the cathode, and together this produces a photocurrent.
TV and remote
Light Sensitive Switch in a circuit
capacitor used in the camera flash for a vintage polaroid
large capacitors such as this are used for storing large amounts of charge
(Inserts cheesy joke)
Why can't you trust an atom?
they make up everything