Created by StemPy LabA heater coil A brings a pot of water to the boil in minutes when connected to the mains on its own. Another coil B does the same in minutes on its own. If both coils are connected in parallel to the same mains, the same pot of water boils in how many minutes? ____
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← An electric kettle rated 1000 W heats 2 kg of water from 20°C to 100°C. Only 80% of the electrical energy goes into the water; the rest heats the kettle and the air. The specific heat of water is 4200 J kg⁻¹ K⁻¹. The time taken, in minutes, is ____.An astronomical telescope has an objective of focal length 100 cm and an eyepiece of focal length 5 cm. It is adjusted so that the final image of a distant star field is formed at the near point of the eye, 25 cm from the eyepiece. Its magnifying power is ____. →
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