How much energy (in kwh) does a light blub that uses 110 v and 0.909 A use in 8.

Question

How much energy (in kwh) does a light blub that uses 110 v and 0.909 A use in 8.00 hours? A 1500-w heater is connected to a 120-v line for 2.0 hours. How much heat energy is produced? A 100-W driveway light bulb is on 10 hours per day. If the power company charges 10 for each kilowatt-hour of electricity used, estimate the yearly cost to operate the bulb if it is used every day for a 365-day year. The resistivity of gold is 2.44 Times 10^-8 Ohm m at a temperature of 20 degree C. A gold wire, 1.8 mm in diameter and 14 cm long, carries a current of 480 mA. What power is dissipated in this wire at 20 degree C?

Explanation / Answer

We will solve it step by step

We are asked to calculate the power dissipated, the expression

P = V I

V = I R

P = I2 R (1)

we calculate the resistance, the expression for the resistance

R = l / A

where

resistivity

l length

A area

Data

= 2.44 10-8 cm

l = 14 cm = 14 10-2 m

D = 1.8 mm = 1.8 10-3 m

The area is a circular wire

A = R2= (D/2)2=

A = /4 ( 1.8 10-3)2

A =2.545 10-6 m

We calculate the resistance

R = 2.44 10-8 14 10-2 / 2.545 10-6

R= 13.422 10-4

With this current value and calculate the power using the expression 1

P = 13.422 10-4 (480 10-3)2

P = 3.09 10-4W

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