Chapter 14: Electromagnetic Induction Flashcards
Electromagnetic Induction, Faraday's Law, Factors affecting induced e.m.f., Flemings Right Hand Rule, Lenz's Law, AC Generator, Transformers, Power Transmission
What is electromagnetic induction?
The production of an induced current or induced e.m.f. in a conductor due to a change in magnetic flux with the conductor
What does Faraday’s law state?
That the magnitude of induced e.m.f. is directly proportional to the rate of change of magnetic flux in the current
What are some factors which affect the strength of the induced e.m.f., and how do they affect the induced e.m.f.?
Strength of magnet: If strength doubles, induced e.m.f. doubles
Number of coils or the number of turns of coils: If number doubles, induced e.m.f. doubles
Relative speed of the magnet or relative frequency of rotation of coils: When speed or frequency doubles, induced e.m.f. doubles
Orientation of magnet or coils: stronger at 90 degrees / perpendicular angle
Area of coil: When area doubles, induced e.m.f. doubles
Winding the coil around soft iron core: When wound around the core, induced e.m.f. increases
Why does induced current not increase when loops of coil are added?
If the number of loops of coil doubles, the area covered by the coil doubles, which doubles the induced e.m.f.. But since the length of coil also doubles, the resistance of the coil doubles. Since V = IR, the current remains unchanged
What does Lenz’s law state?
The direction of the induced current in a closed circuit is such that its magnetic effect opposes the motion producing it
When should Fleming’s Left Hand or Right Hand rule be used?
FLHR is used when the system has a conductor which has current flowing through it, or when power supply is present
FRHR is used when the system has a conductor which does not have current flowing throughh it, or when power supply is not present in the circuit
What does an Alternating Current generator do?
Converts Kinetic energy into Electrical energy
How does an AC generator generate electricity?
As one side of the coil approaches the North pole of the magnet, a North pole is induced at that side of the coil as predicted by Lenz’s law. After passing through the North pole of the magnet, the same side of the coil which have an induced South pole instead, as predicted by Lenz’s law. This will cause the induced current to flip to the opposite direction, causing an alternating current to be generated
What is the purpose of slip rings?
To transfer induced current from the coil to another circuit via carbon brushes, and to ensure the current can flow continously
Why can transformers only work with alternating current?
A transformer requires a constantly changing magnetic field in the primary coil
How do step-up transformers work?
The primary coil has fewer coils than the secondary coil, and the secondary voltage is higher than the primary voltage
How do step-down transformers work?
The primary coil has more coils than the secondary coil, and the secondary voltage is lower than the primary voltage
In ideal transformers, where there is no energy loss, how is the number of turns in each coil related to their voltage and current?
coils in secondary / coils in primary = voltage in secondary / voltage in primary = current in secondary / current in primary
In ideal transformers, where there is no energy loss, how is the power imput and output related?
voltage in primary x current in primary = voltage in secondary x current in secondary
What is the purpose of using a soft iron core in transformers?
Helps to concentrate magnetic field lines, and provides a stronger magnetic flux linkage between primary and secondary coil
