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Physics

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1. Suppose you wish to fabricate a uniform wire out of 1.45 g of copper.

If the wire is to have a resistance R = 0.650 Ω, and if all the copper is to be used, find the following.
(a) What will be the length of the wire?
(b) What will be the diameter of the wire?

2. Gold is the most ductile of all metals. For example, one gram of gold can be drawn into a wire 2.18 km long. The density of gold is 19.3 ? 103 kg/m3, and its resistivity is 2.44 ? 10−8 Ω · m. What is the resistance of such a wire at 20.0°C?


3. The heating element of a coffeemaker operates at 120 V and carries a current of 4.50 A. Assuming the water absorbs all of the energy converted by the resistor, calculate how long it takes to heat 0.415 kg of water from room temperature (23.0°C) to the boiling point.


4. A certain laboratory experiment requires an aluminum wire of length of 25.0 m and a resistance of 2.60 Ω at 20.0°C. What diameter wire must be used? (The resistivity of aluminum at 20.0°C is 2.82 ? 10−8 Ω · m.)


5. A rectangular block of copper has sides of length 17 cm, 21 cm, and 45 cm. If the block is connected to a 4.1 V source across two of its opposite faces, find the following.
(a) What is the maximum current the block can carry?
(b) What is the minimum current the block can carry?

6. If 3.00 ? 10−3 kg of gold is deposited on the negative electrode of an electrolytic cell in a period of 2.99 h, what is the current in the cell during that period? Assume the gold ions carry one elementary unit of positive charge.