Energy dissipation by a resistor


If a current of 4.00 A4.00\text{ A} flows in a copper wire with a cross-sectional area of 2.70×106 m22.70 \times 10^{-6}\text{ m}^2 and a length of 5.40 m,5.40\text{ m}, approximately how much electrical energy is transferred to thermal energy in 15 min?15\text{ min}?

The resistivity of copper is 1.69×108Ωm.1.69 \times 10^{-8}\,\Omega\cdot\text{m}.

Suppose that energy is dissipated at the rate of P1=0.600 WP_1 = 0.600\text{ W} in a resistor which is connected between the terminals of a V1=4.20 VV_1 = 4.20\text{ V} battery. If the same resistor is connected between the terminals of a V2=2.10 VV_2 = 2.10\text{ V} battery, at what rate is energy dissipated?

James dries his hair with a hair dryer every morning. The dryer uses 64 W 64 \text{ W} of power and the current supplied is 0.4 A. 0.4 \text{ A}. What is the resistance of the dryer?

A Nichrome wire that has a cross sectional area of 2.50×106 m22.50 \times 10^{-6}\text{ m}^2 is connected to a potential difference of 75.0 V.75.0\text{ V}. If the wire dissipates 4000 W,4000\text{ W}, what is its approximate length?

Nichrome has a resistivity of 6.00×107Ωm.6.00 \times 10^{-7}\,\Omega\cdot\text{m}.

Consider a certain length of uniform heating wire which has a resistance of R=72Ω.R=72\,\Omega. At what rate is energy dissipated when (a) a potential difference of 360 V360\text{ V} is applied across the full length of the wire, and (b) the wire is cut in half and the same potential difference as in (a) is applied across the length of each half?


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