Ignore writing already on the paper. Carbon is in the semiconductor category of

Question

Ignore writing already on the paper.

Carbon is in the semiconductor category of materials and has a range of resistivity. A resistor itself is 2 cm long and has a cross sectional area of 4 mm^2. What current would flow thru this resistor if it has 120 V across it? A 60 W light bulb is powered by a connection to a wall outlet with 12 V across the plug terminals. a) What is the current passing thru this resistor? b) An incandescent light bulb is typically 2% efficient, meaning 98% of the power goes to generating heat due to resistance. Calculate this resistance. c) If a fluorescent lamp has an effective resistance of 210 ohms, what is its efficiency?

Explanation / Answer

11)

Resistance

R = resistivity x L/A

R = 60x10^-5 x 0.02 /4x10^-6

R = 3 ohm

current flowing through conductor

i = V/R

i = 120/3

i = 40A

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