#62: The rechargeable batteries for a laptop computer need amuch smaller voltage
ID: 1669831 • Letter: #
Question
#62: The rechargeable batteries for a laptop computer need amuch smaller voltage than what a wall socket provides. Therefore, atransformer is plugged into the wall socket and produces thenecessary voltage for charging the batteries. The batteries arerated at 9.0 V, and a current of 244 mAis used to charge them. The wall socket provides a voltage of120 V. (a) Determine the turns ratioof the transformer. (b) What is the current comingfrom the wall socket? (c) Find the average powerdelivered by the wall socket and the average power sent to thebatteries. #15:Two astronauts are 1.30 m apart in their spaceship. Onespeaks to the other. The conversation is transmitted to earth viaelectromagnetic waves. The time it takes for sound waves to travelat 343 m/s through the air between the astronauts equals the timeit takes for the electromagnetic waves to travel to the earth. Howfar away from the earth is the spaceship? #56:An electromagnetic wave strikes a 1.47-cm2section of wall perpendicularly. The rms value of the wave'smagnetic field is 8.35 x 10-4 T. How long does it takefor the wave to deliver 1110 J of energy to the wall?#62: The rechargeable batteries for a laptop computer need amuch smaller voltage than what a wall socket provides. Therefore, atransformer is plugged into the wall socket and produces thenecessary voltage for charging the batteries. The batteries arerated at 9.0 V, and a current of 244 mAis used to charge them. The wall socket provides a voltage of120 V. (a) Determine the turns ratioof the transformer. (b) What is the current comingfrom the wall socket? (c) Find the average powerdelivered by the wall socket and the average power sent to thebatteries. #15:Two astronauts are 1.30 m apart in their spaceship. Onespeaks to the other. The conversation is transmitted to earth viaelectromagnetic waves. The time it takes for sound waves to travelat 343 m/s through the air between the astronauts equals the timeit takes for the electromagnetic waves to travel to the earth. Howfar away from the earth is the spaceship? #56:An electromagnetic wave strikes a 1.47-cm2section of wall perpendicularly. The rms value of the wave'smagnetic field is 8.35 x 10-4 T. How long does it takefor the wave to deliver 1110 J of energy to the wall?
Explanation / Answer
15) The time tS elapsed by sound to travel from the speakerto his friend is: ts=d/vs where d is the distance between two astronauts. The time tEM for the electromagnetic wave to travel from thespeaker to the earth is: tEM=x/c Where x is the unknown distance between the spaceship and theearth; and c is the speed of electromagnetic waves, or the speed of light. We are given that tS = tEM. d/vs=x/c so, x=d(c/vx)=(1.30*3*10^8)/343= 1 137 026.24 m= 1 137.02624 kilometers
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