Magnetism and Electricity Flashcards
(45 cards)
Magnet
A piece of metal that attracts other metals.
Examples of magnetic materials
Iron, nickel and cobalt
Poles
The ends of a magnet. The magnetic force is strongest at the poles. Magnets have a north and south pole. Like poles repel each other. Unlike poles attract each other.
Magnetic Field
The space around a magnet that exerts a force on magnets and magnetic materials.
Compass
A small magnet that moves freely to show direction. The direction the compass needle points to is the direction of the magnetic field lines. Magnetic field lines always run from the north to south pole of the magnet.
Earth’s magnetic field
The core contains a circulating liquid of molten iron and nickel. This circulation creates a magnetic field. It is strongest as the geographic north and south poles. The magnetic poles run in the opposite direction to the geographic poles. This is why a compass points
north - its north pole is attracted to the magnetic south pole.
Importance of the Earth’s Magnetic Field
- Navigation
2. Protection: From streams of energy from the Sun called solar winds.
Current Electricity
A steady flow of charge through wires and circuits.
Static Electricity
Involves electric charge collecting in one place and sometimes suddenly jumping from one place to another.
Conductors
Substances which allow charged particles to flow through them freely, e.g: metals such as copper.
Insulators
Substances that do not allow charged particles to flow through them easily, e.g: rubber and plastic.
Two types of static charges
Positive (+) and Negative (-)
Two negative static charges…
Repel each other
Two positive static charges…
Repel each other
A positive static charge and a negative static charge…
Are attracted to each other
How Lightning Occurs (An Effect of Static Electricity)
The starting point of lightning is in cumulonimbus clouds. These carry a positive charge on top and a negative charge below. Friction between ice particles and water droplets within the clouds causes this charge. The charge built up between the cloud and the ground causes a discharge of giant sparks, which is lightning.
Earthing
When electricity travels through an object into the ground. An earthed object cannot build up a charge.
Components
Objects in a circut which convert electrical energy into other forms, e.g: a motor.
Current and Measuring Current
The rate of flow of charge per second.
The SI unit for electric current is the amphere or amp (A)
Current can be measured using an ammeter.
Potential Difference
When there is a point of high electrical energy and a point of low electrical energy in a complete circut we say that there is a potential difference in electrical potential energy between those points. This provides the energy to push electrons around a circut.
Voltage and Measuring Voltage
Potential difference is also called voltage.
The SI unit for voltage is volts (V).
A voltometer is used to measure the potential difference across a component. It measures the ‘drop’ in energy as energy travels through a component and is converted to other forms.
Cells and Batteries
One ‘battery’ is called a cell. Two or more stacked together make a battery. Both are sources of potential energy. They can transfer their chemical energy into electrical energy. The flow of electric current is from the positive (+) to negative (-) end of the battery.
Structure if a simple cell
Made up of two different metals called electrodes, e.g: copper and zinc, placed in a chemical in the form of a liquid or paste called an electrolyte, e,g: dilute sulfuric acid.
The more cells connected to each other in a battery the greater potential difference of the battery.
Primary Cell
Batteries that cannot be recharged once they are used.
