Upload
covapretic
View
469
Download
2
Tags:
Embed Size (px)
Citation preview
More about electricity an electronics
Unit 6 continuation
ALTERNATING AND DIRECT CURRENT: AC DC
DIRECT CURRENT
It’s the type of current, we get from batteries.
IT’ S ALWAYS THE SAME
ALTERNATING CURRENTIMAGINE A BATTERY CHANGE BETWEEN THE POSITIVE TERMINAL AND THE NEGATIVE.
ALTERNATING CURRENT is the type of current we get from a plug or the main supply.
WE DON’T GET ALWAYS THE SAME VALUE, BECAUSE ELECTRONS CHANGE THE SENSE OF THEIR DIRECTION. THEY CHANGE IT 50 TIMES A SECOND.
WHY WE USE ALTERNATING CURRENT?
• Because this kind of electricity is easier to transport than the direct one
ELECTRIC ENERGY
What was voltage?
• The energy that gives a battery to the electrons to keep then moving through the wire.
• This energy is given to a bulb, a resistor, a buzz, ...
• In these components is transformed into another way of energy.
How can we measure this energy?
• The energy that is consumed by an electrical appliance is calculated knowing the current(I) that pass through it, the voltage (V) that supports and the time working (t):
• E = V · I · t• Unit: Jule, J
Something about electrical appliances
• Motors transform the electricity in movement• Bulbs transform the electricity in light• Resistors transform the energy in heat, so
they are used in heaters
ELECTRIC POWER
• The capacity of an electrical appliance to transform energy in a period of time.
• UNIT: Watt, W
• It can be calculate by : P = V ·I
How can be related energy and power?
• Once we know the power of a receiver, it’s easy to calculate the electric energy consumed by it:
• E = P · t
El kilowatio hora y la factura de la luz
• If you express power in Kw and time in hours, you will get a new unit to energy, kwh.
• These is the unit that measure the consume of energy at home.
ELECTRONIC COMPONENTS
Variable resistors o potentiometers
• It’s a kind of resistor with a value that can be adjusted between a cero and a maximum value given by the manufacturer
Resistor that depends of a physical property• Light Dependent Resistors, LDR, the more light
it receives, the less resistor it has.• Thermistors:– NTC (Negative Temperature Coefficient), the
resistor decreases when the temperature increases
– PTC (Positive Temperature Coefficient), the resistor increases when the temperature increases
light sensor making steps- www.ldrengineering.org, www.circu.flv
• DIODES