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# GCSE Physics - AQA P3 Watch

1. Hi,

Please could someone kindly explain the last topic (P3.3) to me? I would like to know (please) everything from magnetic fields(electromagnets), motor effect, induction and transformers.

Thank you.
2. Firstly, any magnet that can be switched on and off with the click of a button (by turning current on and off) is known as a electromagnet. Electromagnets are usually made of large coils of wiring that carry the current (that are made of highly conductive materials such as copper). An electromagnet requires a constant current to keep a strong stable magnetic field. Electromagnets are used in cranes to lift very heavy pieces of magnetic materials such as cobalt, nickel and iron.

Secondly the motor effect, any wire carrying current inside a magnetic field (e.g. in between 2 permanent bar magnets) will experience a certain force, this force is known as the motor effect. The motor effect works at it' strongest when the wire is 90 degrees to the direction of the magnetic field or perpendicular to it. If the wire is parallel to the magnetic field direction it will not feel any force and if it's between parallel and perpendicular to the magnetic field then the wire will feel some force.

Thirdly, the motor effect can be observed using Fleming's Left Hand rule, where if your thumb is pointing in the direction of the motion of current and your first finger is facing in the direction of the magnetic field direction then your second finger will point in the direction of the force acting on the wire: https://www.google.co.uk/url?sa=i&rc...136024&cad=rjt

Fourthly, electromagnetic induction is when a potential difference (voltage) is induced across a conductor which is experiencing a change in magnetic field. It can be done by moving a magnet in a coil of conductive wiring (copper wiring) or by moving a electric conductor in a magnetic field. To reverse the current or potential difference, the magnet should be moved in the opposite direction or the magnet's polarity should be changed. If the magnet is continuously moved backwards and forwards then it will produce a alternating magnetic field which in turn will induce a alternating current or potential difference and that is how AC current is produced.

Finally, there are 2 types of transformers: Step-Up Transformers and Step-Down Transformers. A transformer has 3 basic parts of it's structure: a primary and secondary coil to step-up and step-down the voltage and a pure iron core which is used to transfer the alternating magnetic field from the primary coil to the secondary coil. Step-Up transformers will step up the voltage to make it easier to carry in power lines and more efficient, step-up transformers have more turns on the secondary coil then the primary coil so that a higher potential difference is induced at the secondary coil and so the voltage is stepped up. Step Down transformers on the other hand will step-down the voltage of electricity that comes from power lines so that it's within UK appliance standards at 230V to then avoid damaging and destroying household appliances. Step-Down transformers have more turns on the primary coil then the secondary coil so that a lower potential difference is induced at the secondary coil and so the voltage is stepped down.

I hope this helped! It took me about 18 mins to type up. Good Luck with the exam today!
3. (Original post by PHInfinity)
Firstly, any magnet that can be switched on and off with the click of a button (by turning current on and off) is known as a electromagnet. Electromagnets are usually made of large coils of wiring that carry the current (that are made of highly conductive materials such as copper). An electromagnet requires a constant current to keep a strong stable magnetic field. Electromagnets are used in cranes to lift very heavy pieces of magnetic materials such as cobalt, nickel and iron.

Secondly the motor effect, any wire carrying current inside a magnetic field (e.g. in between 2 permanent bar magnets) will experience a certain force, this force is known as the motor effect. The motor effect works at it' strongest when the wire is 90 degrees to the direction of the magnetic field or perpendicular to it. If the wire is parallel to the magnetic field direction it will not feel any force and if it's between parallel and perpendicular to the magnetic field then the wire will feel some force.

Thirdly, the motor effect can be observed using Fleming's Left Hand rule, where if your thumb is pointing in the direction of the motion of current and your first finger is facing in the direction of the magnetic field direction then your second finger will point in the direction of the force acting on the wire: https://www.google.co.uk/url?sa=i&rc...136024&cad=rjt

Fourthly, electromagnetic induction is when a potential difference (voltage) is induced across a conductor which is experiencing a change in magnetic field. It can be done by moving a magnet in a coil of conductive wiring (copper wiring) or by moving a electric conductor in a magnetic field. To reverse the current or potential difference, the magnet should be moved in the opposite direction or the magnet's polarity should be changed. If the magnet is continuously moved backwards and forwards then it will produce a alternating magnetic field which in turn will induce a alternating current or potential difference and that is how AC current is produced.

Finally, there are 2 types of transformers: Step-Up Transformers and Step-Down Transformers. A transformer has 3 basic parts of it's structure: a primary and secondary coil to step-up and step-down the voltage and a pure iron core which is used to transfer the alternating magnetic field from the primary coil to the secondary coil. Step-Up transformers will step up the voltage to make it easier to carry in power lines and more efficient, step-up transformers have more turns on the secondary coil then the primary coil so that a higher potential difference is induced at the secondary coil and so the voltage is stepped up. Step Down transformers on the other hand will step-down the voltage of electricity that comes from power lines so that it's within UK appliance standards at 230V to then avoid damaging and destroying household appliances. Step-Down transformers have more turns on the primary coil then the secondary coil so that a lower potential difference is induced at the secondary coil and so the voltage is stepped down.

I hope this helped! It took me about 18 mins to type up. Good Luck with the exam today!
Thank you so much!! Yes, it went okay.

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