Please enable JavaScript.
Coggle requires JavaScript to display documents.
Electromagnetic induction - Coggle Diagram
Electromagnetic induction
Faraday's experiment
It can be concluded that when there is relative motion between the coil and the magnet, then the magnetic field in the coil changes and emf and hence current is induced
Discovery of Micheal Faraday
The process by which current is induced through the action of a magnet in the coil is known as electromagnetic induction
Electricity can be obtained from magnetism, and the current produced is known as induced current
Factors affecting magnitude of induced current
The strength of magnets used
The stronger the magnets, the larger the magnitude of induced current
Number of turns of the coil
Number of turns of the coil increase, the magnitude of induced current increases
Speeds of movement of magnet
The faster the speed of movement of the magnet in and out of the coil, the larger the magnitude of the induced current
Faraday's law of electromagnetic induction
The faraday's law of magnetic induction states that the magnitude of induced current is directly proportional to the rate of change of magnetic flux with the circuit/ rate at which magnetic lines of force are cut
Lenz law of electromagnetic induction
it states that the direction of induced emf, and hence induced current, is always such that its magnetic effect opposes the motion or change producing it.
This can also be proven using the law of COE where electrical energy is produced from the work done against the opposing forces experienced by the moving magnet
Transformers
Transformers are electrical devices that changes the voltage of an alternating current, and they come in various sizes and types
Uses of transformers
Transformers are used in electrical power transmissions from power stations to households and factories
They are used to regulate voltage to ensure the proper operation of electrical appliances
How transformers work
When an a.c flows through the primary coil, it sets up a continually changing magnetic field which induces an a.c in the secondary coil. the induced a.c in the secondary coil allows the bulb to light up
Types of transformers
Step up transformer
The step-up transformer is an electrical device that steps up voltage and is when there are more turns in the secondary coil as compared to the primary coil
Step-down transformer
A step-down transformer is an electrical device that steps down voltage, and is when there are fewer turns in the secondary coil as compared to the primary coil
Improving efficiency of a transformer
By using low resistance copper wires to reduce energy wasted as heat loss
using a laminated core to reduce the flow of eddy current
By using an effective soft magnetic material as the core
Use a specially designed E-shaped core to ensure that the magnetic field produced by the primary coil is completely linked to the secondary coil
Turns ratio
Ns/Np = Vs/Vp = Ip/Is (assuming the transformer is 100% efficient)
Power transmission
Power stations produces a.c. at a voltage of 10000V, and if the electricity were to be transmitted along power lines, there will be a large amount power lost as thermal energy in the cables due to the heating effect, as P=RI^2
Methods to reduce power loss in long distance transmission
Reduce the resistance of the power lines by using thicker wires, so that the power loss as heat is minimal. However, it is not practical as it is heavy and uneconomical to use
To reduce the current in the power lines by stepping up voltage
Alternating current generator
Features of a.c generator
It has 2 permanent magnets
The rectangular coil mounted on an axle is fixed in between the poles of a permanent magnet
2 slip rings are used as sliding contacts with a fixed carbon brush to allow current to flow through
Graph of induced emf against time
Amplitude gives maximum emf induced
frequency is related to the rate of change of magnetic fields: the faster the rate of change of magnetic fields, the higher the frequency
When the speed of rotation is doubled, the magnitude of induced emf is doubled and the frequency is also double. Hence, the output voltage doubles
When the number of turns of the coil is doubled, the magnitude of the induced emf. is also doubled, however, frequency remains constant, the output voltage also doubles