P. 4171. A generator produces electrical power of 40 kW, when operating at a voltage of 2 kV. The load is connected to the generator through a transmission line of resistance 10 .
a) How much power is dissipated during the transmission of electrical energy?
b) Find the efficiency of the transmission of electrical energy.
c) What are the above asked values if at both ends of the transmission lines an ideal transformer is used to step up or step down the voltage. Both transformers can step up or down the voltage by a factor of 10.
P. 4172. With appropriate washing-up liquids the surface tension of water can be significantly decreased. If a frame is immersed into a mixture of water and washing-up liquid, and then it is carefully taken out, there will be a thin layer of soap film on the frame. Coloured stripes can be observed on the soap film (if it is in front of a black background.)
a) What is the direction of the stripes if the plane of the frame is vertical? Why do they have this direction?
b) What is the colour of the film if its width is only 10-8 m?