Study Notes
The magnetic effect of an electric current involves the creation of a magnetic field around a conductor when current flows through it. This effect is used in various applications such as motors and transformers.
- Right hand grip rule — used to determine the relationship between the current and the magnetic field based upon the rotational direction. Example: If the current is upwards, the magnetic field will run in an anticlockwise direction.
- Solenoid — long coil of wire that generates a magnetic field when current passes through it. Example: The magnetic field outside the solenoid is similar to that of a bar magnet.
- Fleming’s left-hand rule — used to predict the direction of force, current, or fields in a magnetic field. Example: The thumb indicates the direction of motion when the index finger points in the direction of the magnetic field and the middle finger points in the direction of the current.
- Electromagnetic induction — process by which a potential difference is induced in a conductor moving through a magnetic field. Example: Moving a wire up and down between magnets induces an e.m.f. in the wire.
Exam Tips
Key Definitions to Remember
- Right hand grip rule
- Solenoid
- Fleming’s left-hand rule
- Electromagnetic induction
Common Confusions
- Direction of magnetic field lines when current direction changes
- Difference between solenoid magnetic field and bar magnet field
Typical Exam Questions
- What happens to the magnetic field when the current in a solenoid is increased? The magnetic field becomes stronger.
- How does the direction of current affect the polarity of the magnetic field? Reversing the current direction reverses the magnetic field polarity.
- What is the role of a commutator in a D.C. motor? It reverses the direction of current every half turn to keep the coil spinning.
What Examiners Usually Test
- Application of the right hand grip rule
- Understanding of electromagnetic induction
- Factors affecting the strength of the magnetic field in a solenoid