THE TOPIC OF TRANSFORMER. PHYSICS SLIDES NOTES FOR FORM 4
- 2. Transformer •The device that changes voltage from one level to another level. •The change can be from higher voltage to lower voltage or lower voltage to higher voltage.
- 4. How does transformer work •If a.c. flows through the primary coil, a.c magnetic field is produced. •This alternating current magnetic fields cuts the secondary coil.
- 5. How does transformer work •If a.c. flows through the primary coil, alternating magnetic field is produced. •This alternating magnetic fields cuts the secondary coil and induces emf in the secondary.
- 6. How does transformer work •This process of inducing e.m.f in the coil of wire by changing current is called mutual inductance.
- 7. Types of Transformers •There are two main types of transformers and these are; a. step-up transformer b. Step-down transformer
- 8. a. Step-up transformer •This changes low voltage to higher voltage or steps up voltage. •The secondary coil has more number of turns than primary coil.
- 10. b. Step-down transformer •This changes high voltage to lower voltage or steps up voltage. •The secondary coil has less number of turns than primary coil.
- 15. Example An alternating e.m.f of 240V alternating current power supply. The primary coil has 1000 turns and 4000 turns on its secondary coil. The secondary coil is 0.2A
- 16. Example Calculate; a. Secondary e.m.f b. Primary current c. Power input
- 17. Example c. Efficiency d. Comment on the answer to (d)
- 20. c. Power input
- 21. c. Power input
- 22. d. Efficiency
- 23. e. Comment on answer of d This is an ideal transformer
- 24. Exercise 1. Transformer has 66 turns in primary coil and 660turns in secondary coil. The voltage in the primary circuit is 240V. Calculate secondary coil voltage?
- 25. Exercise The current in the primary coil of a transformer is 5A and the voltage in primary coil is 220V. The voltage on the secondary coil is 10V.
- 26. Power Losses In Transformer a. Resistance of windings b. Eddy currents c. Self demagnetised d. Leakage of field lines
- 27. a. Resistance of windings As current flows in the coils, wires heat up and energy is lost inform of heat. The heat production in the transformer is due to higher resistance.
- 28. b. Eddy Currents The magnetic field in the transformer changes inducing eddy currents. This heats up the core and energy is lost inform of heat in a transformer.
- 29. c. Hysteresis losses The magnetization and demagnetization of the core requires energy. This energy heats up the core and is lost as heat energy.
- 30. d. Magnetic Leakage/Flux Not all magnetic field lines from the primary coil may reach the secondary coil. The lost magnetic field lines leads to lost of power in a transformer
- 31. Minimize Power Losses a. Resistance of windings b. Eddy currents c. Hysteresis losses d. Magnetic Leakage/Flux
- 32. a. Resistance of windings To minimize this loss of energy thick copper wires of low resistance are used. The thick copper wires have low resistance hence minimizing heat loss .
- 33. b. Eddy Currents To minimize the heat loss the core is laminated and insulated. This reduces the eddy currents induced between laminations.
- 34. b. Hysteresis losses •To minimize this, the core is made up soft magnetic material(soft iron). •This is easy to magnetize and demagnetize, reducing heat losses.
- 35. d. Magnetic Leakage/Flux To minimize this the core is designed in such way that all the magnetic field lines from the primary coil should reach the secondary coil.
- 36. Notes To completely reduce heat losses in a transformer is impossible. The large transformer uses oil to absorb heat, heat reducing overheating.