Chapter 4 - Electricity Flashcards
What is charge?
Charge is a property of a particle or object. There are two types, positive charge and negative charge.
When you bring two charged object together, electrostatic attraction/repulsion occurs. Alike charges repel and unalike charges attract.
What is the charge of an atom?
In a simple atom, protons and neutrons make up the central nucleus. The electrons orbit the nucleus. In an atom, the amount of negatively charged electrons and positively charged protons are the same. This means that an atom has no charge at all, it is neutral as there is no net charge.
What happens when you rub a polythene rod and a cloth?
When you rub the two materials, electrons are transferred from the cloth to the rod. The rod now has a negative charge and the cloth has a positive charge as there are not enough atoms to neutralise the charges.
What happens when you rub a perspex rod and a cloth?
When you rub the two materials, electrons are transferred from the rod to the cloth. The rod now has a positive charge and the cloth has a negative charge as there are not enough atoms to neutralise the charges.
How many electrons are transferred?
Not all electrons are transferred, only some. The total amount of charge in the rod and cloth is always same, charge can’t be created or destroyed just like energy or mass.
Describe how moving charges work.
There is a region around any charge where another charge experiences a force. This region is called a electric field.
Static means stationary or still. Rods repel or attract each other only because they are insulators and on an insulator electrons will stay on the rod once yo have rubbed them.
If you rub a metal rod with a cloth it will also become charged, but the metal is a conductor so electrons can move through it. Any extra electrons will move through the rod, into your hand and then into the Earth.
What is an electric current?
An electric current is the flow of charge/the amount of charge flowing per second. Electrons are charged particles and when you connect a battery to a circuit, it provides a push to make the electrons move. The moving electrons make an electric circuit.
How can you measure current?
Current is measured in amperes (A). Small currents are measured in milliamps (mA) 1mA = 0.001A you can measure current with an ammeter. Each component in a circuit provides resistance to charge.
Name three ways we can model electrical circuits and a basic idea of how they work.
- The Rope Model - In this model one person will move a rope around a circle by pulling it through their hands, like the battery pushing charge, whereas another person will grip the rope gently, like resistance to the flow of charge.
- The Factory and The People Model - In this model, we can represent electric circuits through the idea of a factory making things for a shop. The factory represents the battery, the trucks represent the charge and shops are like the resistance.
- The Water Circuit Model - In this model, the pipes are like the wires, the water is like the charges and the tap is like the resistance.
What happens in a thundercloud?
In a thundercloud, the air moves around, which forms a region that is positively charged and a region that is negatively charged. Negative charges at the bottom of the cloud can make a huge spark as they leave the cloud, we call that spark lightning. A spark an also be produced when the charge moves between positive and negative regions in the cloud.
As air does not usually let current flow through it, it takes a big difference in charge to let the air conduct electricity.
What is electric shock?
Lightning can be quite dangerous, if it strikes a person it can kill them by stopping their heart or burn them The charge will flow to a person’s heart and then to the ground. But, doctors can use shocks to restart a persons heart.
What is earthing through lightning conductors?
Many tall buildings have lightning conductors. A lightning conductor is a thick strip of metal that runs from the top of the building to a baseplate underground, so that if lighting strikes, the electrons will flow to the ground.
What is the danger of fuels in cars and planes?
When planes or cars are refuelled, the friction of the fuel moving through the pipe can cause a charge to build up. This could cause sparks which is dangerous as the fuel could catch on fire.
Fuel pipes are earthed by attaching a metal wire to the pipe This means that any extra charge will flow down to the Earth.
What can happen while making electronic and how do engineers counter this?
When making electronics delicate components can get damaged by built up charge so to counter this, engineers wear special wristbands connected to a metal wire that goes to the ground. Any build up will go to the ground instead of the components.
