The potential difference across a resting neuron in the human body is about 145.

Question

The potential difference across a resting neuron in the human body is about 145.0 mv and carries a current of about 1.410 mA. How much power does the neuron release? The cost of electricity varies widely throughout the United States; $0.120/kWh is a typical value. At this unit price, calculate the cost that would result from each of the following: leaving a 40.0 W porch light on for 2 weeks while you are on vacation Making a piece of dark toast in 3.00 min with a 1000 W toaster. drying a load of clothes in 40.0 min in a 5500 W dryer

Explanation / Answer

1) Power is given by voltage*current = 145 * 10-3 * 1.41*10-3 = 204.5 * 10-6 = 204.5 uW.

2) a) Time = 2*7*24 (weeks*days*hours) = 336 hours. So that 0.040 kW for 336 hours i.e. 13.44 kWh

Total cost = cost per unit kWh * total kWh = 0.12 * 13.44 = 1.61 $

b) time in hour = 3 min = 3/60 = 0.05 hours , power in kW = 1 kW

total kWh = 1*0.05 = 0.05 kWh, hence total cost = 0.12*0.05 = 0.006 $

c) time = 40/60 = 0.67 hours, power in kW = 5.5 kW, total kWh = 5.5*0.67 = 3.67 kWh,

hence cost = 0.12*3.67 = 0.44 $

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