When a transformer was connected to an AC it was found that the primary current was 1A and secondary 2A. (a) What type of transformer is this? (b) If a 1000V AC is applied to the primary, what will be the voltage in the secondary? (c) Transformer does not work in DC. Why?
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Answer:
Transformers do what their name implies—they transform voltages from one value to another (The term voltage is used rather than emf, because transformers have internal resistance). For example, many cell phones, laptops, video games, and power tools and small appliances have a transformer built into their plug-in unit that changes 120 V or 240 V AC into whatever voltage the device uses. Transformers are also used at several points in the power distribution systems. Power is sent long distances at high voltages, because less current is required for a given amount of power, and this means less line loss, as was discussed previously. But high voltages pose greater hazards, so that transformers are employed to produce lower voltage at the user’s location.