* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Energy & Electricity
Survey
Document related concepts
Opto-isolator wikipedia , lookup
Stray voltage wikipedia , lookup
Wireless power transfer wikipedia , lookup
Switched-mode power supply wikipedia , lookup
Buck converter wikipedia , lookup
Power engineering wikipedia , lookup
Voltage optimisation wikipedia , lookup
History of electromagnetic theory wikipedia , lookup
Distributed generation wikipedia , lookup
Electric machine wikipedia , lookup
Ignition system wikipedia , lookup
Mains electricity wikipedia , lookup
Rectiverter wikipedia , lookup
History of electric power transmission wikipedia , lookup
Electrification wikipedia , lookup
Transcript
AC & DC Generators LEARNING OUTCOMES: Recognise the differences between DC and AC and illustrate them diagrammatically Describe how simple generators work using the dynamo effect . DC= DIRECT CURRENT The current flows in one direction, from + to -. Eg, a battery AC = ALTERNATING CURRENT The current keeps reversing direction, since the 2 terminals alternately become + and – Eg, mains electricity (in the UK it alternates 50 times per second, so frequency = 50Hz). If we know how long 1 wave lasts for (the period) then the inverse is the frequency. Eg, waves lasts for 0.1s, so the frequency is 1 / 0.1 = 10Hz. Electromagnetic Induction N The ‘field lines’ have to be cut. No current is produced if the magnet is not moving! If You push a magnet into a coil the electrons in the coil are also given a push. This makes an ‘induced voltage’ Electromagnetic Induction Notice the needle moves in the opposite direction N If You pull a magnet out of the coil the electrons in the coil are once again given a push. This makes an ‘induced voltage’ in the opposite direction How Can You Increase the Size of the Induced Current? 1. Move the Magnet Faster 2. Use a Stronger (not bigger!) Magnet 3. Put more Turns on the Coil We can use a magnet, coil and movement to generate electricity with this device Will it make AC or DC Current? This is a Generator You will have heard them near road works generating the electricity to make the traffic lights and machines work AC Generator Induced current can be increased in 4 ways: 1) Increasing the speed of movement 2) Increasing the magnetic field strength 3) Increasing the number of turns on the coil 4) Increasing the area of the coil Bikes often have Dynamos to make electricity to light a bulb Dynamos are slightly different from generators as they rotate the magnet Power stations & Efficiency LEARNING OUTCOMES: Describe how the dynamo effect is used in conventional power stations to generate electricity: • burning fuel • producing steam • spinning a turbine • turbine turns generator. Be able to use equations to calculate efficiency in a variety of situations. Describe & recognise that there is significant waste of energy in a conventional power station. Transformers LEARNING OUTCOMES: Explain how transformers are used on the National grid to transmit electricity at high voltage to reduce energy waste/costs. Explain how, for a given power, increased voltage reduces current. This will decrease energy waste by reducing heating of cables.