A cable of resistance 12ohm carries electric power from a generator producing 250 kW at 10,000 V. Calculate (i) the current in the cable, (ii) the power lost in the cable during transmission.

A cable of resistance 10 Omega carries electric power from a generator producing 250 kW at 10,000 V . The current in the cable is

In the previous problem , the power lost in the cable during transmission is

Two identical resistors, each of resistance 15ohm are connected in (i) series and (ii) parallel, in turn to battery of 6V. Calculate the ratio of the power consumed in the combination of resistors in each case.

Calculate the resistance of an electric heater of 1 kW if it operates on a 220 V power supply.

Read the following text and answer the following questions on the basis of the same: At power plant, a transformer increases the voltage of generated power by thousands of volts so that it can be sent of long distances through high-voltage transmission power lines. Transmission lines are bundles of wires that carry electric power from power plants to distant substations. At substations, transformers lower the voltage of incoming power to make it acceptable for high volume delivery to nearby end-users. Electricity is sent at extremely high voltage because it limits so-called line losses. Very good conductors of electricity also offer some resistance and this resistance becomes considerable over long distances causing considerable loss. At generating station, normally voltage is stepped up to around thousands of volts. Power losses increase with the square of current. Therefore, keeping voltage high current becomes low and the loss is minimized. Another option of minimizing loss is the use of wires of super-conducting material. Super-conducting materials are capable of conducting without resistance, they must be kept extremely cold, nearly absolute zero, and this requirement makes standard super-conducting materials impractical to use. However, recent advances in super-conducting materials have decreased cooling requirement. In Germany recently 1 km super-conducting cable have been installed connecting the generating station and the destination. It has eliminated the line loss and the cable is capable of sending five times more electricity than conventional cable. Using super-conducting cables Germany has also get rid of the need of costly transformers. Transformers generate waste heat when they are in operation and oil is the coolant of choice. It transfers the heat through convection to the transformer housing, which has cooling fins or radiators similar to heat exchangers on the outside. Flush point is a very important parameter of transformer oil. Flashpoint of an oil is the temperature at which the oil ignites spontaneously. This must be as high as possible (not less than 160^(@)C from the point of safety). Fire point is the temperature at which the oil flashes and continuously burns. This must be very high for the chosen oil (not less than 200^(@)C ). Flush point of an oil is

An inductor of 200 mH, capacitor of 400 mu F and a resistance of 10 ohm are connected in series to an a.c. source of 50 V of varialbe frequency. Calculate (i) angular frequency at which maximum power dissipation occurs in the circuit and the corresponding value of effective current, and (ii) value of Q factor is the circuit.

An electric kettle connected to the 230V mains supply draws a current of 10 A. Calculate: (a) the power of the kettle. (b) the energy transferred in 1 minute.