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# TRANSFORMER CALCULATIONS

## on Jan 04, 2009

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Transformers play an important role in the distribution of electricity-Understanding how transformers are used to alter the voltage of a supply is very important, as they form an important part of all ...

Transformers play an important role in the distribution of electricity-Understanding how transformers are used to alter the voltage of a supply is very important, as they form an important part of all electrical appliances, mobile phone, TV, radio, you just name it. In this slideshare however you will meet basic calculations and hints on how to solve them.

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## TRANSFORMER CALCULATIONSPresentation Transcript

• TRANSFORMER CALCULATIONS GCSE PHYSICS PART 2 BASIC www.sciencetutors.zoomshare.com
• A laptop computer transformer has 220 turns on its primary coil, and 80 on its secondary coil. Write down any 3 useful information can you get from the above
• The mains voltage varies from country to country. A battery charger for a 6 Volt Mobile phone battery has 4000 turns on its primary coil and 100 turns on its secondary. Is this charger made for use in the U.K, where the mains supply voltage is 240V, or for Nigeria, where the supply is at 220V or South Africa where the supply is at 120 V?
• The mains voltage varies from country to country. A battery charger for a 6 Volt Mobile phone battery has 4000 turns on its primary coil and 100 turns on its secondary. Is this charger made for use in the U.K, where the mains supply voltage is 240V, or for Nigeria, where the supply is at 220V or South Africa where the supply is at 120 V? Use the equation: Vs/Vp = Ns/Np
• A university transformer has a primary coil of 1000 turns and a secondary coil of 3000 turns. What will be the voltage out of the secondary coil if we apply 200 V to the primary?
• A TV transformer has 120 turns on its primary coil, and 30 turns on its secondary coil. A 15 volt a.c supply is connected to the primary coil of the transformer. What will be the voltage across the secondary coil?
• A local transformer is used to step-up the voltage from 30000 Volts to 45000 Volts. What happens to current?
• NOTE: If the voltage is raised from 30000 V to 45000 V, the current is proportionally lowered and vice versa.
• TRANS FORMER THEORY BASIC
• In general a Transformer is a passive device which transforms alternating (AC) electric energy from one circuit into another through electromagnetic induction.
• Transformer cores are usually made of ferromagnetic materials.
• A changing current in the primary winding creates an alternating magnetic field in the core of the transformer.
• The core multiplies the magnetic field effect which is then passed through the windings/coil of the secondary.
• An alternating voltage is then induced in each of the secondary coil/winding as a result.
TRANSFORMER FACTS www.sciencetutors.zoomshare.com
• In general, the induced voltage in the secondary winding ( V S ) of a transformer is a fraction of the primary voltage ( V P ) and is given by the ratio of the number of secondary turns to the number of primary turns which is mathematically shown as Vs/Vp = Ns/Np TRANS FORMER EQU ATION