Summary and Exam Tips for Electromagnetism
Electromagnetism is a subtopic of Magnetism and Electromagnetism, which falls under the subject Physics in the Edexcel IGCSE curriculum. This unit explores the relationship between electric currents and magnetic fields. The right-hand grip rule helps determine the direction of the magnetic field around a current-carrying wire. In a solenoid, the magnetic field resembles that of a bar magnet, with the north pole indicated by the thumb when the right hand grips the solenoid in the direction of the current.
An alternating current (A.C.) generator induces an electromotive force (e.m.f.) as a coil spins in a magnetic field, changing the current direction with each rotation. According to Faraday’s Law, the induced e.m.f. is proportional to the rate of change of the magnetic field lines cut by the conductor. The magnetic effect of a current shows that increasing the current strengthens the magnetic field, and reversing the current changes the field's polarity.
A current-carrying coil in a magnetic field experiences a turning effect, which can be enhanced by increasing the coil's turns, current, or magnetic field strength. Fleming’s left-hand rule predicts the direction of force on a current-carrying conductor in a magnetic field, with the force acting at right angles to both the current and the field. Charged particles moving through a magnetic field are deflected due to the force exerted by the field, which can be demonstrated using a cathode ray tube.
Exam Tips
- Understand Key Rules: Familiarize yourself with the right-hand grip rule and Fleming’s left-hand rule to predict directions of magnetic fields and forces.
- Visualize Concepts: Use diagrams to visualize the magnetic field patterns around wires and solenoids, and the operation of an A.C. generator.
- Remember Relationships: Keep in mind that the strength of the magnetic field is proportional to the current, and the direction of the magnetic field changes with the current's direction.
- Practice Calculations: Be comfortable with calculations involving Faraday’s Law and the factors affecting the turning effect on coils.
- Clarify Terms: Use precise language, such as "add more turns to the coil" instead of "add more coils," to describe factors affecting induced potential difference.
