P4a/b - Sparks and The Uses of Electrostatics Flashcards
What causes electrons to be rubbed off from one object onto another?
What do the atoms become?
- Friction.
- Ions.
Fill in the blanks.
When an object loses electrons, it becomes ________ charged.
When an object gains electrons, it becomes ________ charged.
- Positively.
- Negatively.
What happens when a polythene rod is rubbed with a duster?
The duster’s electrons are transferred from the duster to the rod. The duster becomes positive and the rod becomes negative.
Fill in the blanks. Like charges ________. Unlike charges ________.
Repel. Attract.
What happens when a negatively charged rod is brought close to paper, which is neutral?
Electrons in the paper are repelled, leaving the side of paper closest to the rod positive. The rod then attracts the paper.
Name 4 minor problems caused by static electricity.
Clothing often clings if it is made of synthetic fibres or it may give you a minor shock. Dust returns to the surface after dusting because of static electricity. Television screens attract dust. Hair stands on end after brushing.
How is lightning caused?
Static electricity builds up in the clouds. If the build up of charge is large enough there will be a large voltage (potential difference). This causes electrons to flow through the air and a spark occurs.
Name 3 dangers of static electricity.
When refuelling aircraft, friction could cause a build up of static electricity, resulting in a spark which would ignite the vapour from the fuel and cause an explosion. Humans can get an electric shock when removing synthetic clothing or if they become earthed after walking on synthetic carpets. When powders travel along pipes their surface area makes them very reactive, so friction could result in a spark and an explosion.
Name 4 ways that the dangers of static electricity can be overcome.
Objects, such as lorries carrying flammable liquids, can be earthed to allow the electricity to flow to the ground through a wire. Antistatic sprays, liquids or cloths provide a conducting layer which prevents the charges building up. Insulating mats can be used. Workers can wear shoes with insulating soles.
How does a defibrillator work?
The paddles are charged and they are placed on the chest, either side of the heart, so that good electrical contact is made. A charge is passed through the patient to make the heart contract. Care is taken not to give the operator a shock and everyone else stands back to ensure that they do not get shocked.
Name 4 alternative uses of static electricity.
To remove dust particles from power station chimneys before release into the atmosphere. The enable cars to be painted evenly or crops to be sprayed with pesticides. In photocopiers and laser printers. Some dusting brushes become charged so that they attract the dust.
How does an electrostatic dust precipitator work?
Smoke passes through the grid, and it then becomes negatively charged. Therefore, the smoke is attracted to the positive plates. Every so often, a hammer hits the plate, causing the dust to fall off so it is collected.
How is static electricity used to paint cars?
The paint gun is charged, so the paint becomes charged. The paint particles therefore repel to form a fine spray. The car has the opposite charge to the paint, so the paint is attracted to the car. It therefore gives an even coat and reaches the back of the car.
