Question

What are the properties of energy? Give example of electrical, mechanical, chemical, thermal and electromagnetic energies.

Explain Faraday’s law of electromagnetic induction. Does the transformer draw any current when its secondary is open? Can 50-Hz Transformers Be Operated at 60 Hz & Vice versa?

Suppose that cost of electrical energy is $0.32 per kilowatt hour and that your electrical bill for 30 days is $180. Assume that the power delivered is constant over the entire 30 days. (a) What is the power in watts? If the voltage of 230 V supplies this power, (b) what current follows? Part of your electricity load is a 60-W light that is on continuously. (c) By what percentage of can your energy consumption be reduced by turning this light off?

Answer 1

A) Properties of energy:

1. Energy can neither be created nor be destroyed.

2. Energy can only be transformed from one form to another form.

3. The SI unit of energy is the joule, which is the energy transferred to an object by moving it at a distance of 1 meter against a force of 1 Newton.

Examples
1. Electrical Energy: potential energy due to or stored in electric fields.Ex:  Lightening

2. Mechanical Energy: Mechanical energy is the energy a substance or system has because of its motion. Ex: machines use mechanical energy to do work.

3. Chemical Energy: potential energy due to chemical bonds. Ex: Lead Acid Battery

4. Thermal Energy: kinetic energy of the microscopic motion of particles, a form of disordered equivalent of mechanical energy. Ex: solar radiation to cook food.

5. Electromagnetic Energy: potential energy due to or stored in electric & magnetic fields. Ex: Signal transmitted or received by an antenna.

B) Faraday's Law of electromagnetic induction

1st Law:

Whenever a conductor is placed in a varying magnetic field, emf is induced, which is called induced emf; if the conductor circuit is closed, the current is also generated, called induced current.

2nd Law:

The induced emf is equal to the rate of change of flux linkages(flux linkages is the product of turns, n of the coil, and the flux associated with it)

2) The transformer doesn't draw any current due to the 1st Law of Faraday that the current won't flow unless the circuit is closed.

3) Transformers rated at 60Hz should not be used on a 50Hz supply due to higher losses and core saturation and the resultant higher temperature rise. Transformers rated for 50Hz, however, can be operated on a 60Hz supply.

Answer 2

write down the uses of elecric energy