Physics Flashcards
Positive and negative - attracting and repelling
Positive repels positive
Negative repels negative
Positive attracts negative
Negative attracts positive
Which charges do protons, electrons and neutrons have?
Protons have a positive charge
Electrons have a negative charge
Neutrons have no charge
What is an electrical field?
An electric field is around a charge, like a gravitational field around a mass. If you put a charged object in an electric field, a force will act on it.
What is current?
The amount of charge flowing per second. You can measure the current using an ammeter. Current is measured in amps. You can work out the current by potential difference divided by the resistance.
Batteries and cells
Pushes the charge around the circuit. In the wires there are electrons, and when you connect the battery the electrons move. In a torch there a 2 cells; cells used together are called a battery.
What is potential difference?
The cell or battery provides the push to make the charge move, this is the potential difference. The potential difference tells you the size of the force on the charges. You measure it using a voltmeter and it is measured in volts. You do this by connecting a voltmeter across it. This is called the rating. You measure potential difference by current x resistance.
What is a parallel circuit?
In a parallel circuit there is more than 1 loop. The potential difference across each component is the same as the potential difference across the battery.
What is a series circuit?
In a series circuit there is only 1 loop. The potential difference across each component adds up to the potential difference across the battery.
What is resistance
Each component has a different resistance. This tells how easy it is for the charges to pass through the component. It is measured in ohms. The current depends on the resistance of the component and the push of the battery. You can work out the resistance by:
Potential difference divided by the current.
What are conductors.
Metals are good conductors. They have very low resistance because they have lots of electrons that move.
Insulator
Other materials such as plastics do not have many electrons that are free to move, therefore they are not very good conductors.
Attracting and repelling poles
North poles repel north poles
South poles repel south poles
North poles attract south poles
Magnetic fields
You can find out the shape of a magnetic field by using plotting compasses or using iron fillings. If the magnetic field lines are closer together this show the fields are stronger.
Electromagnets
Electromagnets usually have a magnetic materials in the centre of the coil, called a core. If you remove steel from a magnet it stays the same.
Making electromagnets stronger
The number of turns, or loops on the coil.
Increase the amount of current in the wire
Change the type of core to a more magnetic material.
Energy
Different foods are stores of different amounts of energy. Energy is measured in joules.
Conservation of energy
Energy can not be created or destroyed, only transferred. This is called the law of conservation of energy.
Energy store
There is energy associated with food and fuels. This type of energy is known as a chemical store. Energy if transferred from the store when you burn the fuel.
Transferring energy
Electric current, light and sound are ways of transferring energy between stores.
Wasting energy and saving energy
In many situations energy it transferred to the thermal store of the surroundings. This means the energy is dissipated.
