Electrical & Electronic Engineering
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5 Terms
What is energy? What is the unit to describe energy?
Capacity to do work. Joules (J)
What is power? What is the relationship between power and energy? What is the unit of power?
Is the rate of energy transfer, measured in watts (W), which is 1 J/s
Suppose it takes 20 minutes to put 500 litres of petrol into a truck. The specific gravity (or relative density) of petrol is 0.73 kg/l and its heat value is 45 GJ/tonne. How much energy is transferred to the truck? What is the average power?
13.69 MW
Explain the effect of the power factor value on the magnitude of current in a circuit or a power system. Hence, explain the effect of the power factor on the losses in electrical grids.
Since P=I*V*cos(ϕ), rearranging for I would show that it is inversely proportional to the power factor. A lower PF means that more current is required for the same average power. More current means more copper loss (Ploss=I2R)
