HW10Sol - Jim Guinns PHYS2212 Assignment #10 Solutions 1. A...

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Jim Guinn’s PHYS2212 Assignment #10 Solutions 1. A 10 4 carbon resistor used in electronic circuits is rated at 0.25W . a) What maximum current can this resistor carry? The maximum current is I = (P / R) 1/2 = 5mA . b) What maximum voltage can be placed across this resistor? The maximum voltage is V = (P R) 1/2 = 50V . 2. If energy costs 9 cents per kilowatt-hour, 1 kW-hr = (1x10 3 J/s) (3600s) = 3.6x10 6 J . a) How much does it cost to operate an electric toaster for 4 min if the toaster has resistance 11.0 and is connected across 120V? The power dissipated in the toaster is P = V 2 / R = 1.31kW . Operating for 4min (1/15 hr) gives a cost of (1.31kW) (1/15 hr) (9 cents / kW-hr) = 0.79 cents. b) How much does it cost to operate a heater of resistance 5.0 connected across 120V for 8hours? In this case, P = 2.88kW , therefore the cost is $2.07 . 3. a) Find the equivalent resistance between points “a” and “b”. The two resistors in parallel give an equivalent resisance of [(1 / (6
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HW10Sol - Jim Guinns PHYS2212 Assignment #10 Solutions 1. A...

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