Name the type of transformer that converts a low-voltage supply into a high-voltage supply.
step up transformer
True or false? Switch mode transformers use very little power when they are switched on but no load is applied.
Does a step-down transformer increase or decrease the voltage?
This is the national grid. Label Part 1
Step up Transformer
Use for electromagnets
Electromagnets are often used to lift iron and steel scrap in scrapyards.
Are electromagnets a type of permenant magnet?
A TV requires a potential difference of 11.5V and a current of 10A. It uses a transformer to produce the correct potential difference from the mains supply. If the mains supply is 230V, what current does it provide to the transformer?
- A parallel field
Explain how to produce a uniform magnetic field (3)
- Two permenant bar magnets
- Pole pieces arranged correctly e.g north facing south
- make sure magnets are the correct distance apart
When a plastic rod is rubbed with a cloth, the plastic rod gains ........
After the plastic rod has been rubbed with the cloth, the plastic rod has a ........ charge
Electrostatic charges can be useful during paint spraying.
The droplets of paint are given the same charge as they leave the sprayer.
Explain why this is an advantage (2)
- Repel each other
- Droplets spread out
Droplets of paint are positivly charged.
The object being painted is given a negative charge.
Explain why this is an advantage. (2)
- Object attracts droplets
- Less paint wasted
Give one hazard caused by electrostatic charges and state how the risk from this hazard can be reduced (2)
- risk of spark/shock/damage
- reduce the risk by using insulation/earthing
Describe how a loudspeaker uses an electrical supply to produce sound waves [5 marks]
- There is current in the coil
- changing current produces magnetic field
- Interacts with field of permanent magnet
- Using Fleming’s LHR;
- Force on coil
- Making longitudinal waves
State why a metal plate used in an electromagnet device is made of iron (1)
- iron loses its magnetism quickly (not a permenant magnet)
Describe the construction of an electromagnet. You may draw a diagram to help your answer. (3)
- current carrying (insulated) wire
- wrapped into coil
- wrapped on iron core;
Describe the changes that allow the electromagnet to release the door when the fire alarm sounds (2)
- current/ voltage reduces
- (magnetic) force holding the iron plate to the magnet no longer present