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P7 PHYSICS

P7 ELECTROMAGNETISM

QuestionAnswer
What does a moving charge create? A moving charge creates a magnetic field.
What happens when a current flows through a wire? When a current flows through a wire, a magnetic field is created around the wire.
How is the field made up, with the wire in the centre? The field is made up of concentric circles perpendicular to the wire, with the wire in the centre.
What will happen if you place a compass near a wire that is carrying a current? You can see this by placing a compass near a wire that is carrying a current. As you move the compass, it will trace the direction of the magnetic field.
If you change the direction of the current - what will happen and what rule will help you work out the direction of this? Changing the direction of the current changes the direction of the magnetic field-use the right-hand thumb rule to work out which way it goes.
What will happen to the strength of the magnetic field if you change the distance from the wire? The strength of the magnetic field produced changes with the current and the distance from the wire. T
What is a solenoid? A solenoid is a coil of wire.
How can you increase the strength of the magnetic field that a wire produces? You can increase the strength of the magnetic field that a wire produces by wrapping the wire into a coil called a solenoid.
Why is the strength of the magnetic field that a wire produces increased when you wrap the wire into a coil? This happens because the field lines around each loop of wire line up with each other.
Which way will the field lines point and what will the lines be like? Why is this? This results in lots of field lines pointing in the same direction that are very close to each other. The closer together field lines are, the stronger the field is.
What is the magnetic field inside a solenoid like? The magnetic field inside a solenoid is strong.
Outside the coil - what is the magnetic field like? Outside the coil, the magnetic field is just like the one round a bar magnet.
How can you increase the field strength of a solenoid? and why does it do this? You can increase the field strength of the solenoid even more by putting a block of iron in the centre of the coil. This iron core becomes an induced magnet whenever current is flowing.
What will happen to the magnetic field if you stop the current? If you stop the current, the magnetic field disappears.
What is good about electromagnets? Electromagnets have lots of uses. Magnets you can switch on and off are really useful. They're usually used because they're so quick to turn on and off or because they can create a varying force (like in loudspeakers,
Name a use of electromagnets. Electromagnets are used in some cranes to attract and pick up things made from magnetic materials like iron and steel, e.g. in scrap yards.
What can you do to the magnet in an electromagnet? Using an electromagnet means the magnet can be switched on when you want to pick stuff up, then switched off when you want to drop it.
If an electromagnet is used with other circuits - what can it act as? Can you give an example of this? Electromagnets can also be used within other circuits to act as switches (e.g. in the electric starters of motors).
What happens to the field when the current through the wire is larger or you are closer tot he wire? The larger the current through the wire, or the closer to the wire you are, the stronger the field is.
The magnetic field inside a solenoid is uiform - what does this mean? The magnetic field inside a solenoid is strong and uniform (it has the same strength and direction at every point in that region).
What is a an electromagnet? A solenoid with an iron core (a magnet whose magnetic field can be turned on and off with an electric current) is called an ELECTROMAGNET.
Created by: HJB1972
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