"Magnetism, as you recall from physics class, is a powerful force that causes certain items to be attracted to refrigerators." -Dave Barry
Physics is a fundamental subject that can be studied by teenagers in the United Kingdom during their last two years of secondary school.
Many consider the GCSE subject of physics to be the most interesting of the scientific disciplines due to the fact that teachers encourage students to ask questions and then try to answer them by observing and experimenting.
Physics are the study of electricity, forces, waves and atomic. During their studies of the physics topics, students also learn more about the most powerful forces in the universe such as magnetism and electromagnetism.
The AQA exam board, that operates in the United Kingdom, has magnetism and electromagnetism as the seventh topic on its GCSE Physics Syllabus and it is divided into the sections of magnetic fields, electromagnets, electromagnetic induction and transformers.
Superprof is here to create a guide for potential students of the GCSE Physics Syllabus and provide them with all the information that will be covered in this subject in order to help them make an educated decision and decide if this GCSE subject is for them.
Magnetism can be contributed to the magnetic fields that surround magnets. Magnets have two opposite poles, the north-seeking pole of a magnet is known as the north pole and the south-seeking pole is commonly referred to as the south pole.
The magnetic field is always stronger near the magnet's poles either north or south.
Just like other similar concepts of physics, magnetism has rules that need to be memorized by students, such as the following:
- Like poles repel each other, North and North or South and South. For example, if the north pole of the magnet is approached to another north pole it will repel,
- Unlike poles such as North and South or South and North are attracted to each other. Therefore, it is true when experts of love say that opposites attract!
Since this is the seventh topic of the GCSE Physics Syllabus, students have previously studied the topic of forces and understand that magnets are non-contact forces which means that magnets affect each other without touching.
Iron, steel, nickel and cobalt are all magnetic materials that are attracted to either pole of the magnet. Permanent magnets are most commonly made of iron and produce their own magnetic field that cannot be turned off.
Some examples of permanent magnets include tacky fridge magnets your parents always buy you after one of their trips and horseshoe magnets.
These magnets are very different from permanent magnets due to the fact that they only become a magnet when placed in a magnetic field. After it is removed from the magnetic field, its magnetism is quickly lost.
They can only be attracted to other magnets and they cannot repel.
What is a Magnetic Field?
Students learn the basics of a magnetic field in this section of the Physics Syllabus. A magnetic field is known as the region around a magnet where a force acts on another magnet.
While magnetic fields are invisible to the human eye, they can be detected using a small tool known as a magnetic compass.
The needle of the compass has the four cardinal directions (North, East, South and West) and points in the direction of the Earth's or a magnet's magnetic field.
Drawing a magnetic field is a task expected by students undergoing the GCSE Physics Syllabus. Primary characteristics of drawing a magnetic field include the facts that magnetic field lines never touch, closer the lines = stronger the magnetic field and the lines drawn have arrowheads so that onlookers understand in which direction the force is going.
Electromagnets can be observed most often in household devices such as electric bells and door locks that can both be controlled with a remote. The most simple electromagnets are created by coiling wire around an iron nail.
Solenoids are wires coiled up in a spiral shape and play an important part in the creation of an electromagnet due to the fact that a solenoid with an iron core is called an electromagnet.
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The Motor Effect
In this section, students next analyze and calculate the motor effect which is basically two magnetic fields interacting and creating a force that pushes the wire at right angles.
The motor effect can be calculated using the following equation:
force = magnetic flux density x current x length or
Examples and questions are observed by pupils to better understand the use of the motor effect in the scientific discipline of physics.
Fleming's Left-Hand Rule
Sir John Ambrose Flemming of the United Kingdom originated the left-hand rule as a simple way of working out the direction of motion of an electric motor. To follow Fleming's left-hand rule, an individual needs to hold up their thumb, forefinger and second finger at right angles to each other:
- The forefinger is lined up with magnetic field lines that point from north to south,
- The second finger is lined up with the current pointing from positive to negative,
- The thumb shows the direction of the motor effect force on the conductor carrying the current.
An electric motor can be made using the force a coil of wire carries a current into a magnetic field that tends to make it rotate. Electric motors have many different parts that need to be explained in order to correctly understand their function.
The motor effect can also be observed inside headphones due to the fact that they contain small loudspeakers. Variations in an electric current cause variation in the magnetic field. This phenomena causes the cone to move and creates sound waves. Pupils studying this section learn more about how the loudspeaker creates sound waves.
Electromagnetic induction or the generator effect is when a coil of wire is moved in a magnetic field or a magnet is moved in a coil of wire to create a potential difference that is needed to make an electric current flow.
Students also take time to understand more about the current of induced potential and how it depends on the direction of the movement and how the direction is reversed when the magnet is taken out of the coil.
An alternating current generator is a device that produces a potential difference. These generators can be featured in cars and known as alternators which have the purpose of keeping the battery charged and to run the electrical system while the engine is running.
A simple AC generator can be made up of simple elements such as a coil of wire that rotates around a magnetic field.
The output of an alternator can be featured on a potential difference-time graph with the voltage on the vertical axis and time on the horizontal axis.
An AC generator is not the only device that produces a potential difference, the direct current generator does the same. A basic DC generator is made up of a coil of wire rotating in a magnetic field using a split ring commutator.
Some bicycles have a DC generator known as a dynamo that runs the lamps while the wheels are turning.
In a dynamo, the current to the external circuit always flows in the same direction and its output can be observed on a difference-time graph that has the potential difference or voltage on the vertical axis and the time on the horizontal axis.
A microphone converts sound waves into electrical signals. Students analyze the diagram of moving-coil microphones to analyze the different parts and understand the pressure variations in sound waves.
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Transformers are very useful for those living overseas where the voltage is different and they want to use imported appliances or tools.
A transformer is an invaluable device that can change the potential difference or voltage of an alternating current. A step-up transformer increases the voltage and a step-down transformer decreases the voltage.
A basic transformer that is most commonly used is made up of two coils of wire: a primary one from the AC input and a secondary coil to the AC output.
Transformers can only work will alternating current and students learn more about its functions when it is working.
Calculating potential differences can be done using the following equation:
It is also important to note that pupils will learn how to calculate a transformer's power transfer:
power = potential difference x current
The power is measured in watts, the potential difference is calculated in volts and the current is gauged in amps.
Sample Exam Questions
Questions on the assessments from the GCSE Physics Syllabus include many different types of questions that all aim to test the knowledge of students. When pupils decide to take time and analyze examples of the different kinds of questions that will be considered on the examination, they reduce stress and increase performance results.
Here are the types of questions considered on the GCSE Physics Syllabus examination:
- Multiple choice questions: the simplest to complete because all students have to do is read the different options and check the right box,
- One and two mark questions: these questions start off with keywords such as "describe" or "explain" and these questions may have diagrams or graphs to consider,
- Three and four mark questions: practically the same as the aforementioned questions, however, longer answers are required,
- Maths questions: students maths skills are tested and they may sometimes be asked to draw a graph,
- Practical questions: these questions are based on the knowledge acquired while completing the required practical activities,
- Six mark questions: many students find these questions to be the most difficult on the assessment due to the long and logical answers that are required,
- Equations: this part requires test taskers to remember the different equations that were taught during class time.
Learning about some of the most powerful forces in the world, magnetism and electromagnetism, can helpfully prepare students for a future scientific career or provide the acquiring of essential physics topics for those with scientific interests.