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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 on other magnets.
• Magnetic field lines show the shape and direction of a magnetic field, and they point from the north pole to the south pole outside a magnet.
• The magnetic field is strongest where the field lines are closest together, such as near the poles of a bar magnet.
• Opposite magnetic poles attract each other, and like magnetic poles repel each other.
• A magnetic material is a material that is attracted to a magnet, such as iron, steel, nickel or cobalt.
• An induced magnet is a magnetic material that becomes magnetised when it is placed in a magnetic field.
• Induced magnetism usually causes attraction because the end of the magnetic material nearest the magnet becomes the opposite pole.
• The Earth has a magnetic field, so a magnetic compass needle lines up with this field and points roughly towards geographic north.
• 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, and its magnetic field is similar in shape to the field around a bar magnet.
• The magnetic field inside a solenoid is strong and nearly uniform because the fields from each turn of wire add together.
• The strength of an electromagnet increases when the current increases, the number of turns of wire increases, or an iron core is added.
• An electromagnet is temporary because its magnetic field can be switched on and off by switching the current on and off.
• The motor effect occurs when a current-carrying conductor in a magnetic field experiences a force because the two magnetic fields interact.
• The force on a current-carrying conductor is greatest when the conductor is at 90 degrees to the magnetic field and is zero when it is parallel to the magnetic field.
• For a conductor at right angles to a magnetic field, the force is calculated using `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.
• The direction of the force on a current-carrying conductor is reversed if either the current direction or the magnetic field direction is reversed.
• An electric motor uses the motor effect to make a coil rotate in a magnetic field when current flows through it.

• Plot the magnetic field around a bar magnet using a compass, marking the direction of the compass needle at several positions and joining the points to form field lines.
• Draw magnetic field patterns around bar magnets in different pole arrangements, showing arrows from north to south and closer lines where the field is stronger.
• Investigate how magnetic force varies with distance by changing the separation between two magnets, measuring force consistently, and identifying the pattern in the results.
• Draw the magnetic field around a straight current-carrying conductor as concentric circles, using the right-hand grip rule to show the direction of the field.
• Draw the magnetic field of a solenoid, showing a strong uniform field inside the coil and a north and south pole at opposite ends.
• Investigate electromagnet strength by changing one variable at a time, such as current, number of turns or core material, and measuring the effect on lifting force or paper clips picked up.
• Use Fleming’s left-hand rule by placing the first finger in the magnetic field direction, the second finger in the current direction, and the thumb in the force direction.
• Calculate the force on a current-carrying conductor using `F = BIL`, substituting values with correct units and rearranging the equation when required.
• Explain the operation of a simple electric motor by linking the current in the coil, the magnetic field, the forces on opposite sides of the coil, and the resulting rotation.