help The quantity of charge q (in coulombs) that has passed through a surface of
ID: 2137058 • Letter: H
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The quantity of charge q (in coulombs) that has passed through a surface of area 2.10 cm2 varies with time according to the equation q = 8t3 + 4 t + 6, where t is in seconds. What is the instantaneous current through the surface at t = 1.10 s? What is the value of the current density? What is the relationship between current and current density? kA/m2 Need Help? A lightbulb has a resistance of 200 ohm when operating with a potential difference of 150 V across it. What is the current in the lightbulb? The resistance of a lightbulb varies for different values of the applied voltage, but at any particular voltage it has a fixed value as in this problem. What is the equation relating voltage to current? mA Need Help? A certain lightbulb has a tungsten filament with a resistance of 17.7 ohm when at 20.0 degree C and 149 ohm when hot. Assume the resistivity of tungsten varies linearly with temperature even over the large temperature range involved here. Find the tem Need Help? A certain waffle iron is rated at 0.87 kW when connected to a 120-V source. What current does the waffle iron carry? Your response differs from the correct answer by more than 10%. Double check your calculations. A What is its resistance? Your response is within 10% of the correct value. This may be due to roundoff error, or you could have a mistake in your calculation. Carry out all intermediate results to a t least four-digit accuracy to minimize roundoff error. ohmExplanation / Answer
1)b)Currect density=I/A =32.46/2.1A/cm2 =15.45A/cm2 =154.5KA/m2
2)V=IR gives I=150/200 =750mA
4)a)P=VI gives I=870/120 =7.25A
b)P=I^2R gives R=16.55ohm
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