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Transformers 1 of 6 © Boardworks Ltd 2012 Parts of a transformer 2 of 6 © Boardworks Ltd 2012 Using a transformer to change voltage The voltage induced in the secondary (output) coil depends on the number of turns on the primary and secondary coils. A step-up transformer has more turns on the secondary coil and so increases voltage. 3 of 6 A step-down transformer has fewer turns on the secondary coil and so decreases voltage. © Boardworks Ltd 2012 Investigating transformers 4 of 6 © Boardworks Ltd 2012 Properties of transformers Transformers transfer power between circuits. The design of a transformer determines the characteristics of the electricity flowing in its secondary circuit. The frequency of the alternating current in the secondary circuit matches the primary circuit, but what about voltage? The voltage in each circuit is related to the number of coils on each side of a transformer by the following formula: primary voltage secondary voltage Vp Vs 5 of 6 = primary turns secondary turns = Np Ns © Boardworks Ltd 2012 Calculating voltage 6 of 6 © Boardworks Ltd 2012