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Electromagnetic induction (view source)
Revision as of 10:46, 24 August 2014
, 10:46, 24 August 2014→Concept #3 -
===Activities===
===Activities===
==Concept #3 - ==
==Concept #3 FLEMING'S LEFT HAND RULE AND WORKING OF MOTOR - ==
===Learning objectives===
===Learning objectives===
#State Fleming's left hand rule of motor
#Explain working of motor
#Distiguish between dynamo and motor
#Application of the motor
===Notes for teachers===
===Notes for teachers===
Difference between A.C. and D.C
Direct current (D.C.) Alternating current (A.C.)
1. It is the current of constant magnitude.
2. It flows in one direction in the circuit.
3. It is obtained from a cell (or battery)
1. It is the current of magnitude varying with time.
2. It reverses its direction periodically while flowing in a circuit.
3. It is obtained from A.C. generator and mains.
Advantages of A.C. over D.C.:
In India, we use 220 volt a.c. in our houses and factories. The use of A.C. is advantageous over D.C. because the voltage of A.C. can be stepped up by the use of a step-up transformer at the power generating station before transmitting it over the long distances. It reduces the loss of electric energy as heat in the transmission line wires. The A.C. is then stepped down to 220 volt by the use of step-down transformers at the successive sub-stations before supplying it to the houses or factories. If D.C. is generated at the power generating station, its voltage cannot be increased for transmission and so due to passage of high current in the transmission line wires; there will be a huge loses of electrical energy as heat in the line wires.
A.C. Generator D.C. Motor
1. A generator is a device which converts mechanical energy into electrical energy.
2. A generator works on the principle of electrro magnetic inductions.
3. In a generator, the coil is rotated in a magnetic field so as to produce electric current.
4. A generator makes use of two separate coaxial slip rings.
1. A d.c. motor is a device which converts electrical energy into mechanical energy.
2 d.c. motor works on the principle of force acting on a current carrying conductor placed in a magnetic field.
3. In d.c. motor, the current from d.c. source flows in the coil placed in a magnetic field due to which the coil rotates.
4. A d.c. motor makes use of two parts of slip ring (i.e., split rings) which act as a commutatar.
===Activities===
===Activities===
#Activity 1 -
#Activity 1 -
==Concept #4 ==
==Concept #4 ==