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level: Transformers

Questions and Answers List

level questions: Transformers

QuestionAnswer
Transformers: Design & UseTransformer - a device that can change the PD/voltage of an AC (step-up=increase, step-down=decrease) DESIGN: - 2 coils of wire: primary -from the AC input, secondary -from leading to the AC output - The coils aren't electrically connected, but are wound around an iron core which is easily magnetised and can carry magnetic fields from the primary to secondary coil HOW IT WORKS: 1) a primary voltage drives an AC through a primary coil 2) the primary coil current produces a magnetic field which changes the current changes 3) the iron core increases the strength of the magnetic field 4) the changing magnetic field induces a changing potential difference in the secondary coil 5) the induced potential difference produces an alternating current in the external circuit NOTE: the ratio of coils in a transformer match the ratio of PD
Power Transmission- The National Grid carries electricity around Britain - The higher the current in a cable, the greater the energy transferred to the surroundings by heating - This means that high currents waste more energy than low currents. - To reduce energy transfers to the environment, the National Grid uses step-up transformers to increase the voltage from power stations to thousands of volts, which lowers the current in the transmission cables - Step-down transformers are then used to decrease the voltage from the transmission cables, so it is safer to distribute to homes and factories NOTE: The equation for power assumes the transformer is 100% efficient