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| Questão | Responda |
| How can the current from a dynamo can be increased? Give three ways. | The current from a dynamo can be increased by: - using a stronger magnet - increasing the number of turns on the coil - rotating the magnet faster. |
| What can the output from a dynamo be displayed on? | The output from a dynamo can be displayed on an oscilloscope. |
| What does an oscilloscope trace show? | An oscilloscope trace shows how the current produces by the dynamo varies with time. |
| What is the time for one complete cycle called? | The time for one complete cycle is called the period of the alternating current. |
| What is the height of the wave on a oscilloscope trace? | The height of the wave is the maximum (peak) voltage. |
| What the length of the wave on a oscilloscope represent? | The length of the wave represents the time for one cycle. |
| What is the equation for frequency using period? | Frequency = 1 ÷ period |
| What is frequency measured in? | Frequency is measured in hertz (Hz). |
| What is period measured in? | Period is measured in seconds (s). |
| What does a simple generator consist of? | A simple generator consists of a coil of wire rotating between the poles of a magnet. |
| How is a current produced by a simple generator? | - The coil cuts through the magnetic field as it spins. - A current is produced in the coil. |
| How else can a current be produced? | A current can be produced if the coil remains stationary and the magnets move. |
| How do generators at power stations work? | Generators at power stations work on the same principle. |
| How does a turbine drive a generator in a conventional power station? | In conventional power stations, fuels are used to heat water: - water boils to produce steam - steam at high pressure turns a turbine - the turbine drives a generator. |
| How is efficiency a measure of? | Efficiency is a measure of how well a device transfers energy. |
| How is energy in a power station lost? | Energy in a power station is lost in the boilers, generators and cooling towers. |
| What is the equation for efficiency? | efficiency = useful energy output / total energy input |
| PRACTICE QUESTION What is the efficiency of a power station if 60MJ of fuel energy is converted into 20MJ of electrical energy? | efficiency = useful energy output / total energy input efficiency = 20000000 / 60000000 efficiency = 0.33 or 33 % |
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