Curriculum Portal

neurologyYou need to know

• A magnetic field is the region around a magnet or current-carrying conductor where a magnetic force acts on magnetic materials or other magnets.
• Magnetic field lines show the shape and direction of a magnetic field, and outside a magnet they point from the north pole to the south pole.
• The closer together magnetic field lines are, the stronger the magnetic field is at that point.
• Like magnetic poles repel each other, and unlike magnetic poles attract each other.
• A bar magnet has a north-seeking pole and a south-seeking pole, and the magnetic field is strongest near the poles.
• A magnetic compass contains a small magnet that lines up with the Earth's magnetic field and points towards the Earth's magnetic north region.
• The Earth behaves as if it has a giant magnetic field, so a compass can be used for navigation.
• Some magnetic materials, such as iron, steel, nickel and cobalt, can become induced magnets when placed in a magnetic field.
• Induced magnetism is usually temporary in soft iron but can be more permanent in steel.
• The magnetic force between two magnets gets weaker as the distance between them increases.
• A current flowing through a conductor produces a magnetic field around the conductor.
• The magnetic field around a straight current-carrying wire forms concentric circles centred on the wire.
• Reversing the direction of the current reverses the direction of the magnetic field around a current-carrying conductor.
• A solenoid is a coil of wire that produces a magnetic field similar in shape to the field around a bar magnet when a current flows through it.
• The magnetic field inside a solenoid is strong and nearly uniform because the fields from each turn of wire add together.
• An electromagnet is a solenoid, usually with an iron core, that becomes magnetic only when current flows through it.
• Increasing the current, increasing the number of turns on the coil, or adding a soft iron core increases the strength of an electromagnet.
• The motor effect is the force produced when the magnetic field around a current-carrying conductor interacts with an external magnetic field.
• The force on a current-carrying conductor in a magnetic field is greatest when the conductor is at right angles to the field and is zero when it is parallel to the field.
• The size of the force on a current-carrying conductor at right angles to a magnetic field is given by `F = BIL`, where `F` is force in newtons, `B` is magnetic flux density in tesla, `I` is current in amperes, and `L` is length in metres.

• Plot the magnetic field around a bar magnet using a compass, marking the direction of the compass needle at several points and joining the points with smooth field lines from north to south.
• Draw magnetic field patterns for attracting and repelling magnets, showing correct field line direction and stronger fields where the lines are closest together.
• Investigate how the magnetic force between two magnets changes with distance by varying the separation, measuring force consistently, and identifying the relationship from the results.
• Draw the magnetic field around a straight current-carrying conductor using concentric circles and determine the direction using the right-hand grip rule.
• Draw the magnetic field around a solenoid, showing a strong, uniform field inside the coil and field lines leaving the north pole and entering the south pole.
• Investigate electromagnet strength by changing one factor at a time, such as current, number of turns, or core material, and measuring strength using a consistent method.
• Explain how a solenoid strengthens the magnetic effect by linking the coil arrangement to the overlapping magnetic fields from each turn of wire.
• Use Fleming's left-hand rule to predict the direction of the force on a current-carrying conductor, with first finger for field, second finger for current, and thumb for force.
• Calculate the force on a current-carrying conductor using `F = BIL`, including correct substitution, rearrangement where needed, and units.
• Predict how the motor effect changes when current, magnetic flux density, length in the field, or the angle between conductor and field is changed.