Edexcel GCSE Physics 1PH0
Key Concepts of Physics
Motion and Forces
Conservation of Energy
Waves
Light and the Electromagnetic Spectrum
Radioactivity
Astronomy
Energy – Forces Doing Work
Forces and Their Effects
Electricity and Circuits
Static Electricity
Magnetism and the Motor Effect
Electromagnetic Induction
Particle Model
Forces and Matter
Electromagnetic Induction
The transformer turns-ratio equation
- 3 things to know
- Paper 2
Overview
The turns ratio equation, calculating an output voltage or the number of turns on a coil, and telling a step-up from a step-down transformer by its turns.
What you need to know
Answer each one before you reveal it.
A transformer changes 230 V into 11.5 V and has 2000 turns on its primary coil. Calculate the number of turns on its secondary coil.
A transformer with 1200 turns on its secondary coil raises 100 V to 400 V. Calculate the number of turns on its primary coil.
Questions from this subtopic
Each one with the model answer underneath.
- 1
State the turns ratio equation used for a transformer.
Model answer
Primary voltage ÷ secondary voltage = number of primary turns ÷ number of secondary turns.
- 2
A transformer has 200 turns on its primary coil and 1000 turns on its secondary coil. Calculate the output voltage for an input of 12 V.
Model answer
Output voltage = 12 × 1000 ÷ 200 = 60 V.
- 3
A transformer changes 230 V into 11.5 V and has 2000 turns on its primary coil. Calculate the number of turns on its secondary coil.
Model answer
Secondary turns = 2000 × 11.5 ÷ 230 = 100 turns.
- 4
A transformer has 800 turns on its primary coil and 200 turns on its secondary coil. Calculate the output voltage for an input of 240 V.
Model answer
Output voltage = 240 × 200 ÷ 800 = 60 V.
- 5
A transformer with 1200 turns on its secondary coil raises 100 V to 400 V. Calculate the number of turns on its primary coil.
Model answer
Primary turns = 1200 × 100 ÷ 400 = 300 turns.
- 6
A transformer has 500 turns on its primary coil and 2500 turns on its secondary coil. State whether it steps the voltage up or down, and by what factor.
Model answer
It steps the voltage up by a factor of five.
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